Foundation for the multi-account epic (T-476): a Flutter-free AccountRegistry
over the app-scope SettingsStore (per-user, never committed to a repo).
- `app.claude.accounts` — the {name, dir} account list (dir = CLAUDE_CONFIG_DIR).
- `app.claude.account.<hash>` — per-workspace binding to an account name; the
hash is the SAME FNV-1a 64-bit hex D-70 uses for the socket path, trailing
separators stripped so /repo and /repo/ map alike.
- accountForWorkspace(cwd) resolves an account or null (a binding to a removed
account degrades to null = Claude's default, never errors).
- probeExistingAccountDirs(home): read-only bootstrap probe for adoptable
~/.claude-* config dirs (welcome-view UX is T-481).
Keys are app.-prefixed because SettingsStore requires a scope prefix; app scope
already provides the per-user persistence T-483 wants (T-356 will consolidate
more state later but isn't a hard blocker). No spawn/UI/CLI — downstream
tickets. Unit tests cover CRUD, the disk round-trip, hash/trailing-slash
mapping, independent bindings, and probe filtering.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>