When editing a file outside the workspace root, SafeOpenError previously
used the "invalid-path" code with the message "path escapes root". This
was indistinguishable from other invalid-path errors (hardlinks, symlinks,
non-files) and consumers often fell back to a generic "not found" message,
which was misleading.
Add a new "outside-workspace" error code with the message "file is outside
workspace root" so consumers can surface a clear, accurate error message.
- fs-safe.ts: add "outside-workspace" to SafeOpenErrorCode, use it for
all path-escapes-root checks in openFileWithinRoot/writeFileWithinRoot
- pi-tools.read.ts: map "outside-workspace" to EACCES instead of rethrowing
- browser/paths.ts: return specific "File is outside {scopeLabel}" message
- media/server.ts: return 400 with descriptive message for outside-workspace
- fs-safe.test.ts: update traversal test expectations
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
