Go to a folder by name, with g then o

Requested in #233. The `g` shortcuts cover the handful of folders every
account has -- inbox, sent, drafts -- and nothing reaches the dozens a Sieve
rule fills, which is where somebody with a real folder tree spends their time.
`g o` opens the picker, you type part of a name, and you are there.

The picker is the one the move action already uses, with one difference that
only shows up on shared mail: it selected folders by `mayAddItems`, which is
right for a destination and wrong for a place to go. A shared folder you may
read but not file into is somewhere you can visit. The right is now a
parameter, named for what it is asking rather than for which caller wants it.

Hosted in AppShell rather than in the mail view, because the `g` shortcuts are
global and the mail view is not mounted to hear about it -- pressing this from
the calendar should still take you to a folder, and now does.

`o` on its own opens a conversation and does not clash: a pending prefix is
tried before a bare key. That was already true and nothing said so, so there
are now five tests for the sequence machinery -- including that an abandoned
prefix costs the prefix and not the keystroke after it, which is the nicer
behaviour of the two and was undocumented.

Checked in a browser against the mock: opened from the calendar, filtered to a
nested folder, landed on it, and `o` still opened a conversation afterwards.

Closes #233.

web/src/views/Shortcuts.tsx

@@ -7,7 +7,7 @@ import { Dialog } from "@/ui/dialog";
 import { Kbd } from "@/ui/misc";
 import { t } from "@/lib/i18n";
 
-export function useGlobalShortcuts({ onHelp }: { onHelp: () => void }) {
+export function useGlobalShortcuts({ onHelp, onGoToFolder }: { onHelp: () => void; onGoToFolder: () => void }) {
   const [, navigate] = useLocation();
   useEffect(() => {
     const go = (role: string) => () => {
@@ -18,6 +18,15 @@ export function useGlobalShortcuts({ onHelp }: { onHelp: () => void }) {
       { keys: "c", description: "Compose new message", group: "Mail", handler: () => void useCompose.getState().open() },
       { keys: "?", description: "Show keyboard shortcuts", group: "Navigation", handler: onHelp },
       { keys: "g i", description: "Go to Inbox", group: "Navigation", handler: go("inbox") },
+      /*
+       * A folder by name, for a tree the other `g` shortcuts cannot reach. The
+       * ones below are the handful of folders every account has; this is for
+       * the dozens that Sieve fills and that have no letter of their own (#233).
+       *
+       * `o` on its own opens a conversation, which is not a clash: the manager
+       * completes a pending sequence before it tries a single key.
+       */
+      { keys: "g o", description: "Go to folder…", group: "Navigation", handler: onGoToFolder },
       { keys: "g s", description: "Go to Starred", group: "Navigation", handler: () => navigate("/search?q=is:starred") },
       { keys: "g t", description: "Go to Sent", group: "Navigation", handler: go("sent") },
       { keys: "g d", description: "Go to Drafts", group: "Navigation", handler: go("drafts") },
@@ -27,7 +36,7 @@ export function useGlobalShortcuts({ onHelp }: { onHelp: () => void }) {
       { keys: "g f", description: "Go to Files", group: "Navigation", handler: () => navigate("/files") },
       { keys: "g k", description: "Go to Settings", group: "Navigation", handler: () => navigate("/settings") },
     ]);
-  }, [navigate, onHelp]);
+  }, [navigate, onHelp, onGoToFolder]);
 }
 
 export function ShortcutsDialog({ open, onClose }: { open: boolean; onClose: () => void }) {