Feature: Read-only mode (--read-only)

[BrunoO]

Summary

Add a process-wide --read-only CLI flag so the application performs no filesystem write on any drive. All write-related operations are disabled or no-op; UI reflects the mode and greys out disabled actions.

Operations inhibited in read-only mode

• Delete / move to Recycle Bin or Trash — UI disabled; programmatic calls no-op + log warning.
• Saving settings — In-memory changes allowed; no write to settings.json; user informed that changes won’t be saved.
• Export results (CSV, etc.) — Export actions disabled/greyed; no file created.
• Drag-and-drop that would move/copy files — Disabled (e.g. no shell drag-drop data on Windows).
• Quick Access pinning (Windows) — Pin/unpin disabled.
• Logging to FindHelper.log — No log file; use stderr/stdout or in-memory only.
• Index dump (--dump-index-to) — Rejected (error exit or ignore + stderr message); no dump file.
• Any other disk writes — Gated by a central “can write?” check; documented or disabled when read-only.

User-visible behavior

• Small “Read-only mode” indicator in the main window.
• Disabled actions greyed with tooltip: e.g. “Disabled in read-only mode (--read-only); this action would modify files or settings.”
• --help documents the flag.

Spec

Full specification (in development repo): specs/2026-02-24_read_only_read_only_mode_spec.md — requirements, edge cases, platform notes (Windows Shell APIs, etc.), and acceptance criteria.

Scope

All platforms: Windows, macOS, Linux.