Stop a project id from steering a Docker API DELETE, and stop trusting a store that lost its list

C-2 (critical). `destroy_ownerless_rollback_pin` validated its tag and not its
project id, then interpolated both into `triple-c-snapshot-{id}:{tag}` and handed
the result to bollard. bollard does not percent-encode: `Uri::parse` joins an
absolute path onto the base URL, which replaces the path outright and applies RFC
3986 dot-segment removal. An id of `a/../../v1.47/volumes/<name>?` turns a
"remove image tag" into `DELETE /v1.47/volumes/<name>`. That arm is reached
*because* `find_project` failed, so the id is unconstrained IPC input, and the
typed confirmation is no barrier — it compares the caller's own two strings.

Reproduced against the live daemon, and now a test: with the check removed the
volume is gone and the test fails; with it, the volume survives and a legitimate
ownerless pin still deletes. The reference that reaches `remove_image` is now the
daemon's own repo_tag, matched on the parsed pair, so nothing built from IPC
input addresses the API at all. The same id check now guards the owned arms of
`destroy` and `compact_snapshot`, which build volume names and image references
from a `projects.json` field.

H-1. The ownerless arm decided ownership from the in-memory list alone and then
called `sweep_orphaned_snapshots()`, which deletes the freshly dangling image on
the same pass — so a corrupt `projects.json` could reap a pin whose migration is
still awaiting confirmation, the one thing `pin_is_reapable` orders its
conditions to prevent. It now re-reads the store from disk, runs
`project_store_trust`, refuses an id the store knows, takes the project lock
before reading anything a decision rests on, and checks `has_record`.

H-3. The corrupt-store guard keyed on "empty list + file exists", and
`ProjectsStore::new()` swallows a corrupt file without rewriting it — so the
first `save()`, as little as starting a project, wrote `[{new}]` over it and the
guard passed with every other project's volumes unclaimed. A corrupt load is now
recorded in a sticky `projects.json.corrupt` marker beside the file, and the
existing `.bak` is no longer clobbered by a second corruption. A missing
`projects.json` is refused too: it cannot be told from a moved or partially
restored data directory, and the genuinely fresh case has nothing to find.

Also: the three migration commands surface the lock's real refusal instead of
substituting "a migration is already running"; `note_ownerless_since` re-checks
`has_record` after writing a tombstone, closing the window that could plant one
behind a valid record and reap the pin with zero grace; corrupt migration-record
copies are capped at four; `reconcile_migration` yields to any lock holder, not
only a migration; and a 22-space run in a refusal string is gone.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GBq2rGum6GX7xXgsas1fDc

app/src-tauri/src/docker/migration.rs

@@ -1233,6 +1233,14 @@ pub async fn reap_stale_migration_pins() -> usize {
             }
             // Records the first sighting when there is none, which is why this
             // returns `None` on that pass and the pin survives it.
+            //
+            // A `save` can land between the `has_record` above and this write,
+            // which would plant a tombstone dated *now* behind a perfectly
+            // valid record — invisible until that record is legitimately lost,
+            // at which point the pin is already past its grace period and is
+            // reaped on the first check. `note_ownerless_since` re-asks
+            // `has_record` after the write and removes the marker again; the
+            // reasoning for why that closes the window is on it.
             let ownerless_since =
                 crate::storage::migration_store::note_ownerless_since(&project_id, &tag, &now);
             if !pin_is_reapable(&tag, has_record, ownerless_since, &now) {