[Bug]: Cannot downgrade nightly to stable; channel switch does nothing and manual downgrade hides existing chats

Area

apps/desktop

Steps to reproduce

1. Running nightly 0.0.29-nightly.20260722.875 (stable is 0.0.28).
2. Switch update channel from nightly to stable, restart.
3. Manually replace the AppImage with the staged 0.0.28 build, relaunch.

Actual behavior

Step 2: 0.0.28 gets downloaded to ~/.cache/t3code-updater/pending/ but is never installed. The app stays on the nightly. 0.0.29-nightly is a higher semver than 0.0.28, so the updater won't apply it.

Step 3, on 0.0.28: projects and chat threads show up missing/wrong in the UI.

state.sqlite is intact throughout (checked read-only): orchestration_events = 64148 rows through the current session, projection_threads all present with correct titles, projection_thread_messages = 5808 rows, effect_sql_migrations = 15, all projectors in projection_state caught up to the max sequence.

Restoring the nightly 0.0.29 AppImage and relaunching brings all projects and chats back. No data was lost; the threads are just not surfaced by 0.0.28.

Looks like the same class as #4261 (OrchestrationGetSnapshotError: Thread <id> was not found after a version change with events still present). Possibly related: #961, #2181.

Version or commit

0.0.29-nightly.20260722.875 downgraded to 0.0.28.

Environment

Ubuntu 22.04.5 LTS, x86_64, Desktop AppImage, nightly channel, Claude provider, local.

Start by reproducing the update-channel switch and manual AppImage downgrade in apps/desktop, then inspect the updater's pending path and state.sqlite projections. Confirm that switching from nightly to stable installs the stable version and that existing projects and chats remain surfaced on 0.0.28 without altering the stored data.