JSON.parse('/path/to/file') throws SyntaxError, crashing the viewer and
any code reading observations with legacy bare-path data in those columns.
- Add parseFileList() helper in observations/files.ts — tries JSON.parse,
falls back to wrapping bare strings in an array
- Replace unsafe JSON.parse calls in files.ts, SessionStore.ts, ChromaSync.ts
- Add 9 unit tests covering null, empty, valid JSON, bare paths, invalid JSON
Closes#1359
Co-Authored-By: Claude <noreply@anthropic.com>