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/env.ts

@@ -21,8 +21,21 @@ export const getGlobalClaudeFile = memoize((): string => {
     return join(getClaudeConfigHomeDir(), '.config.json')
   }
 
-  const filename = `.claude${fileSuffixForOauthConfig()}.json`
-  return join(process.env.CLAUDE_CONFIG_DIR || homedir(), filename)
+  const oauthSuffix = fileSuffixForOauthConfig()
+  const configDir = process.env.CLAUDE_CONFIG_DIR || homedir()
+
+  // Default to .openclaude.json. Fall back to .claude.json only if the new
+  // file doesn't exist yet and the legacy one does (same migration pattern
+  // as resolveClaudeConfigHomeDir for the config directory).
+  const newFilename = `.openclaude${oauthSuffix}.json`
+  const legacyFilename = `.claude${oauthSuffix}.json`
+  if (
+    !getFsImplementation().existsSync(join(configDir, newFilename)) &&
+    getFsImplementation().existsSync(join(configDir, legacyFilename))
+  ) {
+    return join(configDir, legacyFilename)
+  }
+  return join(configDir, newFilename)
 })
 
 const hasInternetAccess = memoize(async (): Promise<boolean> => {