[codex] harden desktop persistence and model catalog

[xiaokaige1130-maker]

What changed

• fix runaway Codex global-state backups and retain only the newest 20
• use atomic state writes and owner-aware workspace locks
• move full project refresh out of the systemd state-change service
• remove the redundant 60-second startup polling loop
• add a durable GPT-5.6 custom model catalog feature for rebuilds
• point the updater submodule at the maintained fork commit with npm reliability fixes

Root cause

registerWorkspaceRoot dropped its options argument, so refresh operations created a loose global-state backup for every remembered project. Frequent refresh and watcher runs accumulated more than 22,000 files.

Impact

The desktop now starts with a lightweight synchronous workspace restore, refreshes indexes in the background, and relies on the systemd path watcher for later state changes. Rebuilds retain the GPT-5.6 model allowlist without embedding provider credentials.

Validation

• node --test scripts/project-memory.test.js linux-features/custom-model-catalog/test.js (8 passed)
• node --check scripts/project-memory.js
• bash -n scripts/*.sh
• cargo test -p codex-update-manager codex_cli::tests --no-fail-fast (18 passed in the submodule)
• Linux/Copilot patch suite (199 passed)
• cold desktop restart with Electron, app-server, and port 5175 healthy