When native bindings (better-sqlite3, hnswlib-node) are not available
(common with npx or remote execution), the commands now fall back
gracefully to JSON-based storage instead of crashing.
## Changes
### hive-mind.js (bin/ and src/)
- Made better-sqlite3 import dynamic with loadSqlite() helper
- initHiveMind: Falls back to JSON storage when SQLite unavailable
- showStatus: Shows status from JSON fallback when SQLite unavailable
- Provides clear messaging about npx/fallback mode
### memory.js
- detectMemoryMode: Better error handling for hnswlib/sqlite errors
- handleReasoningBankCommand: Catches native binding import errors
- Silent fallback to basic JSON mode when bindings unavailable
## Testing
- `hive-mind init` creates JSON fallback when SQLite unavailable
- `hive-mind status` shows fallback status correctly
- `memory stats` works without native bindings
- `memory store/query` work with JSON fallback