#21181: fix(models): add gemini-3.1-pro-preview forward-compat for google-gemini-cli provider

## Summary - **Problem:** `gemini-3.1-pro-preview` launched 2026-02-19 and works via the standalone Gemini CLI (`gemini -m gemini-3.1-pro-preview`), but OpenClaw rejects it with `Unknown model: google-gemini-cli/gemini-3.1-pro-preview` because pi-ai's built-in model catalog doesn't include it yet. - **Why it matters:** Users on `google-gemini-cli` cannot use the new model until the catalog is updated. - **What changed:** Added a `resolveGeminiCli31ProPreviewForwardCompatModel` forward-compat resolver in `src/agents/model-forward-compat.ts` that clones `gemini-3-pro-preview` as `gemini-3.1-pro-preview` — the same pattern used for `claude-opus-4-6`, `glm-5`, and `gemini-3-pro-image` in the existing codebase. - **What did NOT change:** No behavioral changes for any other provider or model. ## Change Type (select all) - [x] Bug fix - [ ] Feature - [ ] Refactor - [ ] Docs - [ ] Security hardening - [ ] Chore/infra ## Scope (select all touched areas) - [ ] Gateway / orchestration - [ ] Skills / tool execution - [ ] Auth / tokens - [ ] Memory / storage - [ ] Integrations - [ ] API / contracts - [ ] UI / DX - [ ] CI/CD / infra ## User-visible / Behavior Changes - `google-gemini-cli/gemini-3.1-pro-preview` now resolves to a cloned `gemini-3-pro-preview` model definition, unblocking users who upgraded the Gemini CLI and set the new model in their config. ## Security Impact (required) - New permissions/capabilities? No - Secrets/tokens handling changed? No - New/changed network calls? No - Command/tool execution surface changed? No - Data access scope changed? No ## Repro + Verification 1. Set an agent's model to `google-gemini-cli/gemini-3.1-pro-preview` 2. Send a message 3. Before fix: `Unknown model: google-gemini-cli/gemini-3.1-pro-preview` 4. After fix: routes to Gemini CLI using `gemini-3-pro-preview` metadata as template ## Compatibility / Migration - Backward compatible? Yes - No config or migration changes required. ## Closes Closes #21176 🤖 AI-Assisted: Yes (via OpenClaw) <!-- greptile_comment --> <h3>Greptile Summary</h3> Adds forward-compatibility support for `gemini-3.1-pro-preview` model in the `google-gemini-cli` provider. The model launched on 2026-02-19 and works via the standalone Gemini CLI but isn't yet in pi-ai's built-in catalog. The implementation clones `gemini-3-pro-preview` as a template using the same pattern established for other forward-compat models (`claude-opus-4-6`, `glm-5`). The change is minimal, isolated, and follows existing architectural patterns correctly. <h3>Confidence Score: 5/5</h3> - This PR is safe to merge with minimal risk - The implementation follows an established pattern used for multiple other forward-compat models in the same file. The change is isolated to a single function that only affects the specific `google-gemini-cli/gemini-3.1-pro-preview` model combination. The template model (`gemini-3-pro-preview`) exists and is referenced throughout the codebase. No behavioral changes for other models or providers. - No files require special attention _{Last reviewed commit: d54bce3} <!-- greptile_other_comments_section --> <!-- /greptile_comment -->