Restore beta database migration compatibility

[Obed0101]

Problem

v0.1.44-beta.14 omitted the previously released 20260912160000_todo_target_lock migration identity. Databases used by beta.11 and later therefore fail closed before migration with Unsupported database migration, even though their schema is intact.

Solution

• Restore the original target-lock migration SQL with its exact timestamp and SHA-256 identity.
• Add a regression that verifies the published identity and confirms compatibility inspection leaves database bytes unchanged.
• Document the compatibility repair for v0.1.44-beta.15.

Existing databases that already applied this migration recognize it without rerunning it. New databases create the same previously published table.

Verification

• bun test test/storage/compatibility.test.ts test/installation/rollback.test.ts --timeout 30000 — 12 passed, 0 failed.
• bun run typecheck — passed.
• Local 0.1.44-beta.15 build loaded 29 migrations and passed --version / --help smoke checks.
• Against a consistent isolated SQLite backup: compatibility reported compatible: true, pending: [], legacy: false; the compiled binary listed a session successfully; PRAGMA quick_check remained ok; and the database SHA-256 remained unchanged.

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