Add filesystem watching and reconciliation for SQLite indexes

[DandyLyons]

Goal

Implement md-utils index watch ./notes/ with initial reconciliation and incremental refresh. Part of #93; depends on #138.

Requirements

Use native filesystem change notifications, not read/access events. Debounce changes, handle atomic saves and path changes, and reconcile affected scopes when events are missing or ambiguous. Watch relevant configuration/type/schema inputs as well as document files. Reuse the update service and coordinate concurrent writers. Exclude the index database and its sidecars from scanning/event feedback loops.

Acceptance criteria

• Watch refresh reuses Bound collection refresh memory and reuse extraction across scopes #147's bounded staging/publication service and honors Add optional body indexing with single-copy FTS5 storage #146's persisted indexing mode.
• Database sidecars and staging/recovery files are excluded from discovery and event feedback loops.
• Initial reconciliation completes before normal watching.
• Create/edit/delete/atomic-save events update the index.
• Lost or ambiguous events trigger reconciliation.
• Unreadable scopes do not become deletions.
• Configuration changes invalidate relevant assessments.
• Shutdown/interruption and concurrent CLI updates have defined behavior.

Move identity preservation is deferred. Native platform support and fallback behavior must be documented.