fix: rename .claude.json to .openclaude.json with legacy fallback (#582)

* fix: rename .claude.json to .openclaude.json with legacy fallback

Rename the global config file from ~/.claude.json to ~/.openclaude.json,
following the same migration pattern as the config directory
(~/.claude → ~/.openclaude).

- getGlobalClaudeFile() now prefers .openclaude.json; falls back to
  .claude.json only if the legacy file exists and the new one does not
- Add .openclaude.json to filesystem permissions allowlist (keep
  .claude.json for legacy file protection)
- Update all comment/string references from ~/.claude.json to
  ~/.openclaude.json across 12 files

New installs get .openclaude.json from the start. Existing users
continue using .claude.json until they rename it (or a future explicit
migration).

* test: add unit tests for getGlobalClaudeFile migration branches

Covers the three cases:
- new install (neither file exists) → .openclaude.json
- existing user (only legacy .claude.json exists) → .claude.json
- migrated user (both files exist) → .openclaude.json

---------

Co-authored-by: Zartris <14197299+Zartris@users.noreply.github.com>

src/utils/deepLink/registerProtocol.ts

@@ -253,7 +253,7 @@ async function resolveClaudePath(): Promise<string> {
  * Check whether the OS-level protocol handler is already registered AND
  * points at the expected `claude` binary. Reads the registration artifact
  * directly (symlink target, .desktop Exec line, registry value) rather than
- * a cached flag in ~/.claude.json, so:
+ * a cached flag in ~/.openclaude.json, so:
  *   - the check is per-machine (config can sync across machines; OS state can't)
  *   - stale paths self-heal (install-method change → re-register next session)
  *   - deleted artifacts self-heal
@@ -311,7 +311,7 @@ export async function ensureDeepLinkProtocolRegistered(): Promise<void> {
   // EACCES/ENOSPC are deterministic — retrying next session won't help.
   // Throttle to once per 24h so a read-only ~/.local/share/applications
   // doesn't generate a failure event on every startup. Marker lives in
-  // ~/.claude (per-machine, not synced) rather than ~/.claude.json (can sync).
+  // ~/.claude (per-machine, not synced) rather than ~/.openclaude.json (can sync).
   const failureMarkerPath = path.join(
     getClaudeConfigHomeDir(),
     '.deep-link-register-failed',