[rpranjan11]

find_missing_jsonls_in_backup.py was the only script not updated in
commit 0609930. diagnose.py and repair_session_metadata.py both
received native macOS/Linux path detection but this one was missed.

This PR applies the same _default_appdata_claude_dir() pattern already
used in repair_session_metadata.py for consistency, and restores the
PROJECTS_DIR constant that sits alongside it.

Tested on macOS (MacBook Pro M3). Output matches expected results.

[github-actions]

Thanks for your first PR. Please confirm:

• CI passes (fixture tests + sanitisation lint)
• If you added a mutator, it has a matching fixture and passes the five mutator gates (see docs/architecture.md)
• No personal paths, real UUIDs, or identifying info in committed files

[rpranjan11]

Thanks for your first PR. Please confirm:

• CI passes (fixture tests + sanitisation lint)
• If you added a mutator, it has a matching fixture and passes the five mutator gates (see docs/architecture.md)
• No personal paths, real UUIDs, or identifying info in committed files

CI commit check passes (✅ 28bad99). Fixture test workflows are awaiting maintainer approval to run — nothing I can action on my side.

Confirming the checklist:

• CI: green commit check, fixture workflows pending maintainer approval to run
• Mutator: not applicable — this is a read-only script, no mutator added
• Personal info: diff contains only import platform and the _default_appdata_claude_dir() function — no personal paths, UUIDs, or identifying info