Compat tests: dry-run the harness, and say so when the admin can't log in

None of the eight had ever executed, so all eight ran against an empty store
with synthetic inputs. The plumbing works: the documented JSON shapes parse,
and NO_INSERT stops each one before the harness touches the store, which a
sentinel file in each store directory confirmed — it survived every run,
including the one launched without NO_INSERT.

Two things the runbook got wrong, both of which would have cost a day on the
day the copy exists:

- TMPDIR is the copy's parent, not the copy. The harness opens
  $TMPDIR/<test name>, so a TMPDIR pointing at the copy gets an empty store
  created beside it and the test calls INBUXA's data missing.
- masked_email_compat and undelete_compat need INBUXA_COMPAT_MASKS and
  INBUXA_COMPAT_ARCHIVED, which only the tests' doc comments mentioned.

Every run ended on a 401 raised as "Missing list in response", which reads
as INBUXA's data being wrong when the login is what's wrong. Each test now
authenticates once first and names the variable that failed.

docs/spec/compat-tests.md

@@ -1,6 +1,6 @@
 # Running the compat tests against a copy of INBUXA's data
 
-Status: 2026-09-19.
+Status: 2026-09-19 (dry run below; still unrun against INBUXA data).
 
 Each feature spec has one **(compat)** acceptance test: the check that
 INBUXA's own data opens in inbuxa-server and reads back as it did on the
@@ -20,11 +20,20 @@ tests are not an exception.
 ## What you need
 
 1. A copy of the data store, opened with the same `STORE` backend the copy
-   was taken from, and a `TMPDIR` pointing at it. `NO_INSERT=1` stops the
-   harness from resetting or seeding it.
-2. `INBUXA_COMPAT_ADMIN`, as `name:password`, for a server-level
+   was taken from. **`TMPDIR` is the copy's parent, not the copy.** The
+   harness opens `$TMPDIR/<test name>` (`tests/src/utils/temp_dir.rs`), so
+   the copy for `tenant_compat` has to sit at `$TMPDIR/tenant_compat`, the
+   one for `scim_compat` at `$TMPDIR/scim_compat`, and so on. Point `TMPDIR`
+   at the copy itself and the harness quietly creates an empty store beside
+   it and the test reports INBUXA's data as missing — a cutover blocker that
+   isn't one. Each test wants its own copy anyway: `monitoring_compat`
+   purges what it reads.
+2. `NO_INSERT=1`, which stops the harness resetting and seeding the store.
+   Every one of the eight refuses to run without it, before the store is
+   touched (verified, "The dry run" below).
+3. `INBUXA_COMPAT_ADMIN`, as `name:password`, for a server-level
    administrator in that copy.
-3. For `tenant_compat` only: `INBUXA_COMPAT_EXPECTED`, a JSON file recorded
+4. For `tenant_compat` only: `INBUXA_COMPAT_EXPECTED`, a JSON file recorded
    from the Enterprise server before the move:
 
    ```json
@@ -34,11 +43,18 @@ tests are not an exception.
                                   "domains": ["<id>"]}}
    }
    ```
+5. For `masked_email_compat` only: `INBUXA_COMPAT_MASKS`, recorded the same
+   way:
+   `[{"id": "...", "accountId": "...", "email": "...", "enabled": true}]`.
+6. For `undelete_compat` only: `INBUXA_COMPAT_ARCHIVED`, the
+   `x:ArchivedItem/get` results, each with its `id` and `accountId`:
+   `[{"id": "...", "accountId": "..."}]`.
 
 ## Running one
 
 ```
-NO_INSERT=1 STORE=<backend> TMPDIR=/path/to/copy \
+# the copy is at $TMPDIR/<test name>, e.g. /srv/compat/tenant_compat
+NO_INSERT=1 STORE=<backend> TMPDIR=/srv/compat \
 INBUXA_COMPAT_ADMIN='[email protected]:<password>' \
 RUST_MIN_STACK=8388608 \
 cargo test -p tests --features <backends> <test name> -- --ignored --exact
@@ -60,6 +76,31 @@ Run them one at a time: each starts a server on fixed ports.
 | `scim::scim_compat` | 7, SCIM | No domain open to SCIM, and no account with an `externalId`, as observed |
 | `directory::per_domain::per_domain_directory_compat` | 9, per-domain directories | No directory, no server default, and no domain with its own directory: any domain with one is a cutover blocker |
 
+## The dry run
+
+None of the eight has ever run against INBUXA's data, so on 2026-09-19 all
+eight were run against an empty store with synthetic inputs, to prove the
+plumbing before the day the copy exists. What that established:
+
+- **`NO_INSERT` protects the copy.** A sentinel file was left in each store
+  directory. Every run kept it, and the run without `NO_INSERT` stopped at
+  "NO_INSERT must be set, or the copy of INBUXA's data is wiped" before the
+  harness deleted anything. The guard is ahead of the store in all eight.
+- **`TMPDIR` is the parent.** The store appeared at
+  `$TMPDIR/<test name>/rocks.db` in every run, which is where the finding in
+  "What you need" comes from.
+- **The documented JSON shapes parse.** The three files above, written
+  exactly as this page gives them, were read without complaint by
+  `tenant_compat`, `masked_email_compat` and `undelete_compat`.
+- **A bad administrator now says so.** Each test authenticates once before it
+  asserts anything, and fails with `INBUXA_COMPAT_ADMIN did not authenticate
+  as <name>` and the 401 body. Before that check the first call simply
+  panicked with "Missing list in response", which reads like INBUXA's data is
+  wrong when the login is what's wrong.
+
+What it can't establish is anything about INBUXA's data: every run ended at
+the authentication check, since an empty store holds no such administrator.
+
 ## What a failure means
 
 - `tenant_compat`, `masked_email_compat`, `undelete_compat`,