fix: prune removed models from enabled scope

[y4ho0]

Summary

• prune stale canonical provider/modelId entries from global enabledModels when the model dialog removes those configured models
• support exact entries with thinking-level suffixes while preserving globs, fuzzy or bare model ids, and unmatched future references
• clear enabledModels when every exact entry was removed
• invalidate the model-list cache after the settings update so stale warnings cannot be re-cached

Why

Saving the model dialog updated models.json but never updated settings.json. Exact enabled-model entries for a deleted connector therefore produced a persistent “No models match pattern” warning in every later session.

The cleanup compares the normalized configuration before and after the save. It only removes a canonical entry when that exact model existed in the old config and is absent from the new one. User-authored patterns that may target built-in or future models are left untouched.

Validation

• focused model-config and pruning tests: 8 passed
• full suite excluding the environment-dependent proxy test: 590 passed
• changed-file ESLint and git diff --check: passed
• the full suite’s sole failure is an HTTP proxy tunnel 502, reproduced unchanged on origin/main
• TypeScript checking is currently blocked by the existing ThemeColor assertion in lib/rpc-manager.ts, also reproduced on origin/main

Closes #560