Write down what the last week's features actually do

FEATURES.md had nothing on three of them. The scheduling panel and what it
will not show, the filter editors no longer discarding work in silence,
and where compose-as-new can be reached from — including the reply strip,
which is the one a thumb finds.

KNOWN-ISSUES.md gains the free/busy finding, which is the sort of thing
that page exists for: it was checked against the live server rather than
assumed, free/busy between accounts turns out to need no sharing set up,
and a principal offers no route to its calendars at all. Also what the
check did *not* settle, and which way ihasmail errs in the meantime.

ROADMAP.md gains the two things left deliberately unbuilt: a scheduling
view you can visit with no event in hand, and per-message actions from the
message list on a touchscreen, where the gesture that would open them
already means "select".

KNOWN-ISSUES.md

@@ -46,6 +46,8 @@ works the same way — and dropped where 0.15 was the whole subject. Support for
 - **Self-service credentials** — the registry path is **confirmed live** against Stalwart 0.16.19 (2026-08-25): app passwords created and revoked, password changed, 2FA enabled and disabled, with the browser session surviving the switch to an app password. The 0.15 REST path was confirmed live too, on 0.15.5 (2026-08-24), and has since been removed along with the rest of 0.15 support. The mock enforces the same rules the real server does (current password required, password policy, a TOTP code on every request once 2FA is on, app passwords exempt from it). Password changes are refused by Stalwart for accounts backed by an external directory (LDAP/SQL/OIDC); the server's own message is shown when that happens.
 - **Scheduled send needs one setting turned on, and says nothing when it is off.** Stalwart advertises the delay in the account's `urn:ietf:params:jmap:submission` capability — `maxDelayedSend: 2592000` (30 days) and `FUTURERELEASE` among its `submissionExtensions`, and note it is the *account* capability, not the session-level one, which is empty. But the MTA only honours a hold when `futureRelease` is set under the session's MTA extensions, and [that setting defaults to `false`](https://stalw.art/docs/ref/object/mta-extensions/). With it off, Stalwart takes the `HOLDUNTIL` parameter, skips the hold and sends the message immediately **without an error** — the capability still says thirty days. So set `futureRelease` (to the longest hold you want to allow) before relying on this; a value shorter than 30 days is fine, and a request past it is refused honestly, with a `forbiddenMailFrom` naming the limit. `npm run dev:mock:no-future-release` reproduces the silent-drop case. ihasmail asks for the delay the way JMAP requires — a `HOLDUNTIL` parameter on the envelope's `mailFrom`, since RFC 8621 makes `sendAt` read-only and server-derived — and files the held message in a **Scheduled** folder, because `onSuccessUpdateEmail` would otherwise drop it in Sent the moment the submission is created. Nothing moves it out when the hold expires, so ihasmail reconciles the folder on the way in: released messages to Sent, cancelled ones back to Drafts. Three fixes this depends on landed in **0.16.17**, below the live instance's 0.16.19: `HOLDUNTIL` taking RFC 3339 date-times again (0.16.16 had it wanting Unix timestamps), `EmailSubmission/query` on `undoStatus` agreeing with `/get` about held submissions, and `EmailSubmission/get` without `ids` iterating the right index. The hold itself is now **confirmed against the live 0.16.19** (2026-08-25), once `futureRelease` was set to `30d` there: a submission carrying a `HOLDUNTIL` ten minutes out came back `pending`, with `sendAt` equal to the time asked for and a `250 2.1.5 Queued` from the MTA, rather than going out at once. Worth repeating that the capability is no evidence either way — it advertised `maxDelayedSend: 2592000` and `FUTURERELEASE` while the setting was still off. Only a submission tells you. The rest of the journey is **confirmed live too (2026-08-26)**: a hold expired and was delivered, and the **Scheduled** folder reconciled on the way in — a released message moved to Sent, a cancelled one back to Drafts. Nothing in Stalwart does that moving, so if ihasmail is never opened again the message still goes out; it is only the folder that waits to be tidied.
 - **Stalwart 0.16 and RFC 8984 disagree about the calendar vocabulary, and the server only says so half the time.** A participant's address lives in `calendarAddress`, not RFC 8984's `sendTo`/`email`; the organizer is `organizerCalendarAddress`, not `replyTo`; and a recurrence is a single `recurrenceRule`, not a `recurrenceRules` array. Addressed the RFC's way, `CalendarEvent/set` **keeps the event and discards the whole participant map without an error** — guests disappeared on save and no invitation was ever sent, which is what [#26](https://github.com/Coffey-Labs/ihasmail/issues/26) reported. The array form of the rule is refused honestly, with `invalidProperties`, so recurring events could not be created at all and existing ones showed no repeat ([#30](https://github.com/Coffey-Labs/ihasmail/issues/30)). ihasmail now writes Stalwart's names and reads either, and the mock refuses what the real server refuses, since advertising the RFC spelling is precisely how this got as far as a live server. Verified against 0.16.19 on 2026-08-25, end to end: participants, organizer and rule all survive a create, an update and a re-read; an invitation to an external Gmail address arrived as an invite card, and the decline came back and was applied to the event (`needs-action` → `declined`, sequence 1). Cancelling the event notified the guest too. Adding guests to an event that had none, and clearing them again with `null`, both work on the update path, as does RSVP — which patches `participants/{key}/participationStatus` (and `participationComment`) rather than sending the whole map. That patch had to be aimed at the base event: through 0.16.19 `CalendarEvent/set` refused a synthetic id with *"Updating synthetic ids is not yet supported"*, which is why RSVP resolves `baseEventId` first. 0.16.20 accepts one, so that resolution is now a choice rather than the only option — an RSVP aimed at an occurrence would answer for that date alone. It still resolves the base, which is the answer people mean. Adding a *new* participant by patch is refused as well (`Patch operation failed`), so a changed guest list is written as the whole `participants` property. One more thing to know when reading this code: an expanded occurrence carries a `recurrenceId` but *no* rule of its own, and `baseEventId` is set on everything an expanded query returns — a one-off included, whose own id differs from its base — so neither is a test for recurrence.
+- **Free/busy between accounts needs no sharing, and calendar contents cannot be reached at all.** These are the two halves of the same finding, and the second is what makes the first safe. **Confirmed live on 0.16.20 (2026-09-01)** against the deployed instance: `Principal/getAvailability` was called for all seven principals the directory returns, none of whose calendars are shared with the calling account, and every one was answered — no `forbidden`, no error of any kind, from a server that refuses a malformed call instantly. It returns real data rather than a polite empty list: the caller's own principal reported one busy period against the one event in the next sixty days. And a `Principal` carries only `id`, `type`, `name`, `description` and `email` — **no `accountId`** — so there is no handle with which to ask for anybody's calendars. Free/busy is therefore not the weaker of two permissions, it is the only channel between two accounts, and it is open by default. That is the right posture and worth recording, because a client that assumed sharing was a precondition would hide a working feature behind a setting nobody needs to touch. **One thing this did not settle**: the other six principals reported nothing over a nine-month window, which is equally consistent with "those accounts have empty calendars" — likely, since the session reaches one account — and with "an unreadable principal answers with an empty list rather than an error". Distinguishing them needs a second account with an event in it, and until somebody has one, ihasmail assumes the pessimistic reading everywhere it matters: a participant it cannot read is drawn as unknown rather than as free.
+
 - **An override can move an occurrence, and then `start` and `recurrenceId` mean two different times.** The slot stays where the rule put it and only the clock time moves. **Confirmed live on 0.16.20 (2026-08-31)**: one occurrence of a weekly 09:00 series moved to 14:00 came back `start: 2027-06-14T14:00:00` with `recurrenceId` still `2027-06-14T09:00:00`. This is the right behaviour and it is the reason `recurrenceId` is the handle ihasmail holds: it is the one name for an instance that survives *both* a renumbering and a move, so a mutation can always be re-resolved from it. Worth recording because the mock got it wrong in the other direction — it overwrote an override's `start` with the slot time, so a moved occurrence did not move, and per-occurrence *time* editing looked broken against the mock and correct against the server. Found by asking a real server rather than by reading the mock, which is the only way this kind of disagreement ever surfaces.
 
 - **A synthetic id is only true until the next write, and a stale one is wrong rather than invalid.** Stalwart's expanded-occurrence ids encode a position in the series, and writing a `recurrenceOverrides` entry adds a component that renumbers it. **Confirmed live on 0.16.20 (2026-08-31)**: a five-week series came back as `e i m q u` over 03-01 … 03-29; one override written to 03-08 left the *same five ids* addressing 03-01, 03-15, 03-29, 03-08 and 03-22. Nothing was rejected and nothing reported a change — `i` simply meant a week later than it had a moment earlier. So an id cached across a write silently points at another date, and a delete meant for one occurrence removes a different one. This is the second time the same shape of problem has cost a live debugging session, and it is worth saying plainly why it is dangerous: the failure is not a `notFound` a client would notice, it is a confident answer about the wrong day. ihasmail therefore never mutates an occurrence by an id it is holding. `recurrenceId` is the stable name for a slot in a series — it is the date — so `updateEvent` and `destroyEvent` look the current id up by it immediately before they act, and refuse outright if the date is no longer in the series rather than falling back to the id in hand. The mock renumbers too, by a different permutation to the real server's but with the property that matters, since a mock that kept ids stable would agree with precisely the belief that is wrong.