Harden automatic memory and maintenance for v1.2.2

[aoright]

What changed

• Validate automatic memory using the user's original evidence only; reject questions, transient UI feedback, implementation requests, and other non-durable content.
• Prevent generated titles or summaries from promoting project memory into a global scope.
• Add an auditable memory-quality review that demotes noisy automatic memories to candidates without deleting history.
• Add bounded SQLite busy timeouts, WAL size limits, safe checkpoints, and post-backup WAL truncation.
• Add exact, mode-aware backup retention with a dry-run default and explicit --apply.
• Preserve the v1.2.1 project-resolution fixes: required workspace scope, safe Antigravity fallback resolution, automatic Git workspace registration, project-partitioned FTS, MCP auditing, and SearXNG retry fallbacks.
• Update package metadata, manifests, documentation, and Windows/macOS release naming to v1.2.2.

Safety

• Project retrieval remains isolated and fails closed when the workspace cannot be resolved uniquely.
• Global memory requires an explicit global or cross-project statement in the user's own evidence.
• Memory-quality cleanup is reversible: affected records become candidates and retain audit/history entries.
• Backup pruning previews the exact targets and reclaimable bytes before deletion; each backup mode retains at least one copy.
• WAL checkpoints use short busy timeouts and do not wait indefinitely for active MCP readers.

Verification

• 75 source and packaged unit/integration tests pass locally.
• Release manifests verify for the macOS and Windows 1.2.2 archives.
• Live memory-quality review completed with no remaining active automatic-memory quality warnings.
• Live WAL checkpoint reduced the database WAL from approximately 1.5 GB to approximately 12 KB.
• Backup retention was previewed, applied, and re-previewed: 3 full and 6 critical backups remain, with all retained SHA-256 checks passing.
• Cross-platform GitHub Actions validates macOS/Windows tests and clean-install smoke checks.