fix(models): drop shut-down Gemini preview slugs from the AI Studio catalogs

[MaxFreedomPollard]

What does this PR do?

_PROVIDER_MODELS["gemini"] (hermes_cli/models_catalog_static.py:174) offers two Google AI Studio slugs that Google has shut down: gemini-3-pro-preview and gemini-3.1-flash-lite-preview.

Both sit in the "Previous models" table on https://ai.google.dev/gemini-api/docs/models, introduced by:

These models are deprecated and will be shut down soon; migrate to newer models to prevent service interruptions.

and each is titled (Shut down) in that table:

Gemini 3.1 Flash-Lite Preview (Shut down) — Our most cost-efficient multimodal model, offering the fastest performance for high-frequency, lightweight tasks. gemini-3.1-flash-lite-preview

Gemini 3 Pro Preview (Shut down) — Our state-of-the-art reasoning model, with advanced multimodal understanding. gemini-3-pro-preview

Their only table-mates are gemini-2.0-flash and gemini-2.0-flash-lite — which this repo already treats as dead, in _GOOGLE_HIDDEN_MODELS (agent/models_dev.py:781) under the comment "Stale/retired Google slugs that 404 on the current endpoints". So the two shut-down preview slugs get the same two-part treatment the 2.0 pair got:

1. off the curated picker list, and
2. into _GOOGLE_HIDDEN_MODELS, so _should_hide_from_provider_catalog() also strips them from the live models.dev merge (list_agentic_models, agent/models_dev.py:797) — otherwise the picker re-acquires them from upstream metadata the moment the catalog is reachable, which is exactly why the 2.0 entries need both halves.

Scope is deliberately narrow. gemini-3.1-pro-preview is not touched: it is still a current Preview model on that page, not a "Previous model", and the test pins that. Other hosts keep their own catalogs — vertex, kilocode, ai-gateway, gmi and the google/…-prefixed entries in opencode-go are unchanged, as is model_setup_flows.py.

Related Issue

No issue. Adjacent, non-conflicting: #62746 ("Config-driven override for the Gemma picker-visibility filter") also touches agent/models_dev.py, but it reworks the Gemma half of the filter into config; it neither edits the retired-slug block nor the curated gemini list. This PR adds two entries to the existing frozenset and leaves the filter mechanism alone.

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 🔒 Security fix
• 📝 Documentation update
• ✅ Tests (adding or improving test coverage)
• ♻️ Refactor (no behavior change)
• 🎯 New skill (bundled or hub)

Changes Made

• hermes_cli/models_catalog_static.py: _PROVIDER_MODELS["gemini"] drops gemini-3-pro-preview and gemini-3.1-flash-lite-preview.
• agent/models_dev.py: the same two ids join _GOOGLE_HIDDEN_MODELS, on the "Stale/retired Google slugs that 404 on the current endpoints" line with the 1.5 and 2.0 slugs.
• tests/hermes_cli/test_gemini_shut_down_preview_slugs.py (new): both ids are hidden for provider gemini and google; neither is on the curated list; gemini-3.1-pro-preview stays listed, stays out of the frozenset, and stays visible.

How to Test

1. On main, apply only the test file: scripts/run_tests.sh tests/hermes_cli/test_gemini_shut_down_preview_slugs.py → 2 failed, 1 passed:

   E  AssertionError: gemini-3-pro-preview
   E  assert False is True
   E   +  where False = _should_hide_from_provider_catalog('gemini', 'gemini-3-pro-preview')
   
   E  AssertionError: gemini-3-pro-preview
   E  assert 'gemini-3-pro-preview' not in ['gemini-3.8-flash', 'gemini-3.7-flash', 'gemini-3.1-pro-preview', 'gemini-3-pro-preview', 'gemini-3.6-flash', 'gemini-3.1-flash-lite-preview']
   

2. On this branch: 3 passed.

3. Wider sweep — all 12 test files referencing either slug, _GOOGLE_HIDDEN_MODELS, or the curated gemini list (includes test_gemini_provider.py, test_vertex_model_picker.py, test_gmi_provider.py, test_gemini_native_adapter.py, test_usage_pricing.py): 460 passed, 0 failed.

4. Manually: hermes /model on a Google AI Studio key no longer offers either slug, with or without a live models.dev catalog; gemini-3.1-pro-preview still appears.

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate — searched open and closed PRs for gemini-3-pro-preview, gemini-3.1-flash-lite-preview and _GOOGLE_HIDDEN_MODELS; none retires these slugs (Config-driven override for the Gemma picker-visibility filter #62746 is the only _GOOGLE_HIDDEN_MODELS hit, see Related Issue). No recent commit on either file touches these lines.
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run the touched test file through scripts/run_tests.sh: all passed
• I've added tests for my changes
• I've tested on my platform: macOS 26, Python 3.12
• ruff check on the touched files: All checks passed!

Documentation & Housekeeping

• I've updated relevant documentation — N/A (curated picker data + the existing hidden-slug set)
• I've updated cli-config.yaml.example if I added/changed config keys — N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows — N/A
• I've considered cross-platform impact — N/A (no file I/O or process changes)
• I've updated tool descriptions/schemas if I changed tool behavior — N/A