Gemini handler extracts model from URL path, not JSON body, so
rewriting the request body alone wasn't sufficient for model mapping.
- Add MappedModelContextKey constant for context passing
- Update routes.go to use NewFallbackHandlerWithMapper
- Add check for valid mapping before routing to local handler
- Add tests for gemini bridge model mapping
- Added `gpt_5_1_prompt.md` and `gpt_5_codex_prompt.md` to document Codex instruction guidelines.
- These detail the behavior, constraints, and execution policies for GPT-5-based Codex agents in the CLI environment.
* feat(config): add pruning of stale YAML mapping keys during config save
* Revert watcher.go in "fix: enable hot reload for amp-model-mappings config"