Stabilize menubar refresh and remove Codex release pins

[acgxv]

Summary

• negotiate the installed Codex app-server capabilities at runtime instead of pinning a release, executable digest, or schema digest
• keep the last usable account state visible while background refresh runs
• keep route controls stable and anchor the panel to the clicked menu-bar item
• rebuild the latest local schema and restore the live account registry

Validation

• Swift tests: 216 passed
• decodex-postgres: 42 passed
• decodex-codex: 55 passed
• decodex-runtime: 212 passed, 2 ignored
• decodex-protocol: 67 passed
• latest-schema vNext gate: passed
• live install: 6 accounts ready; 3 available and 3 depleted

The Decodex internal wire contract remains versioned for message-format safety; the user-installed Codex release is not allowlisted.