Create doctor bundles for corrupted graph databases

[jununfly]

Summary

Completes the roadmap-sliced loop for issue #671: doctor --bundle can now create a local diagnostic bundle even when .zcodegraph/zcodegraph.db is malformed.

• Adds a corrupted-status fallback inside diagnostic bundle creation so the bundle path does not require opening the broken database.
• Records replay-safe DB metadata: presence, size, mtime, sanitized open error, diagnostic record availability, graph health, and exact recovery commands.
• Marks graph stats as unavailable with unavailableReason: "corrupted" and surfaces Graph health: corrupted in the bundle summary.
• Adds regression coverage for the malformed DB path and privacy constraints.
• Records the completed roadmap under docs/plans/2026-07-02-corrupted-doctor-bundle-v2-roadmap.*.
• Adds an Unreleased changelog entry for [cli-status-doctor-semantics] 1-3-2 corrupted diagnostic bundle v2 #671.

Verification

• npx vitest run __tests__/status-json.test.ts __tests__/rust-hybrid-doctor.test.ts
• npm run build
• git diff --check

All passed locally.

Boundaries

• No release or publish work is included.
• This does not auto-clean or rebuild corrupted indexes; it only creates a local diagnostic bundle and reports exact recovery commands.