Warn when a live provider CLI catalog diverges from the snapshot #745

Parent: #738
Ship after the snapshot updates (#740, #741, #742). Does not block adding Sol / ultra / ultracode.

Why

electron/providers.js is a handwritten snapshot of each CLI catalogue. It goes stale the moment a model ships. That is how GPT-5.6 Sol, Codex ultra, Claude ultracode, and the OpenCode Zen churn (#742) went missing from the picker even though Custom... already accepts the id.

Keep snapshots as the offline default (no network at picker open). Add a divergence warning so the next miss is visible in-app instead of a research thread.

What to ship

1. When providers.list (or the config doctor) can cheaply read a local CLI cache, compare live ids to the snapshot:
   • Codex: ~/.codex/models_cache.json (visibility=list only)
   • Grok: grok models / ~/.grok/models_cache.json
   • OpenCode: opencode models
   • Cursor: cursor-agent --list-models
   • Kimi: ~/.kimi-code/config.toml [models."..."] alias keys
   • Claude: only if a logged-in CLI has a cheap /model listing; claude --help does not enumerate models. Skip rather than guess.
2. Surface a doctor row or a providers.list note when live has ids the snapshot lacks, or the snapshot still lists ids the CLI no longer does. One line per harness, not a toast on every composer open.
3. Do not auto-merge live ids into the picker in this issue. Merging would also pull visibility=hide models, paid OpenCode providers, and Cursor's 200-id explosion into the default list. Snapshot remains the curated picker; Custom... remains the escape hatch.
4. Never probe the network. Local cache / local models command only. Missing cache = no warning.

Out of scope

• Live-refreshing the picker (optional later, not this issue).
• Treating Cursor's baked-in effort suffixes as a separate effort pill.
• Closing the custom-id path. setProvider must keep accepting any non-empty id up to 100 chars; the snapshot is a suggestion.

Files

electron/providers.js, electron/doctor.js / electron/configDoctor.js (whichever already lists provider CLIs), electron/test/ for the comparison helper.