Fix: Content DB persistence for --continue
Removes the broken `isFreshStart()` logic that was deleting the content store DB on every session restart — even with `--continue`. Old cleanup flags from previous sessions accumulated and triggered false fresh-start detection.
New approach: Content DB always persists. Freshness is handled by:
- 24h TTL — stale content re-fetched automatically
- 14-day cleanup — old DBs and sources deleted on startup
- `force: true` — manual re-fetch when needed
- `source` filter — search scoped to specific indexed content
No more race conditions between startup/resume hooks.
Full diff: `v1.0.30...v1.0.32`