feat: upgrade MiniMax model references to M3

[octo-patch]

Summary

• Problem: The MiniMax example agent and the gateway's OpenRouter fallback samples still pointed at MiniMax-M2.7 by default. MiniMax-M3 has been released, so the default reference should track the latest generation.
• Why it matters: Users copy-pasting examples/beginner/minimax_example.py or the OpenRouter fallback snippets get the older model unless they edit by hand. Documentation and tests were also out of sync.
• What changed: Switch the example default to MiniMax-M3, refresh the OpenRouter fallback snippet to minimax/minimax-m3, update related fixtures and the model-allowlist test. Keep MiniMax-M2.7 and MiniMax-M2.7-highspeed as still-supported options for backward compatibility.
• What did NOT change (scope boundary): TTS / speech configuration, API base URL, env variable names (MINIMAX_API_KEY), Anthropic / OpenAI providers, anything outside MiniMax model identifiers.

Change Type

• Documentation
• Tests
• Chore/infra

Scope

• Tests
• Documentation
• CLI / utilities (example agent)

User-Visible / Behavior Changes

• Running examples/beginner/minimax_example.py now talks to MiniMax-M3 by default (previously MiniMax-M2.7). Users on M2.7 can still pass id="MiniMax-M2.7" explicitly.
• The documented OpenRouter fallback example references minimax/minimax-m3.

Security Impact

• New permissions/capabilities? No
• Secrets/credentials handling changed? No
• New/changed network calls? No (same https://api.minimax.io/v1 endpoint, same MINIMAX_API_KEY)
• Database schema/migration changes? No
• Authentication/authorization changes? No

Verification

Steps to Test

1. rg -n "MiniMax-M" examples/beginner/minimax_example.py tests/unit/test_minimax_example.py — confirms MiniMax-M3 is the default and MiniMax-M2.7(-highspeed) is still allow-listed.
2. uv run pytest tests/unit/test_minimax_example.py — static checks on the example pass against the new model id.
3. rg -n "minimax/minimax-m" gateway/.env.example gateway/src/config/loader.ts gateway/tests/provider/openrouter-body-injection.test.ts — fallback fixture aligned.

Expected Behavior

• test_example_uses_minimax_m3 and the OpenRouter fallback unit test pass.
• test_valid_minimax_models accepts the refreshed allow-list.

Compatibility / Migration

• Backward compatible? Yes — M2.7 / M2.7-highspeed still work; only the default identifier changed.
• Config/env changes? No
• Database migration needed? No

Risks and Mitigations

• Risk: Users with hard pinning in their own scripts to MiniMax-M2.7 won't be affected (we kept it allow-listed); only the example default changed.
  • Mitigation: M2.7 / M2.7-highspeed remain documented and asserted in the test allow-list.

Checklist

• Tests updated alongside code
• Documentation updated (in-file comments / docstrings)
• Backward compatibility considered

Summary by CodeRabbit

• Documentation

  • Updated beginner examples and configuration documentation to reference MiniMax M3 model

• Tests

  • Updated test suite to validate MiniMax M3 model integration

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 199a14e4-8a07-4c7a-a5c9-549eab79b6ce

📥 Commits

Reviewing files that changed from the base of the PR and between 682a19c and 142c756.

📒 Files selected for processing (5)

• examples/beginner/minimax_example.py
• gateway/.env.example
• gateway/src/config/loader.ts
• gateway/tests/provider/openrouter-body-injection.test.ts
• tests/unit/test_minimax_example.py

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📝 Walkthrough

Walkthrough

This PR updates the MiniMax model reference from M2.7 to M3 across the beginner example, configuration documentation, and all test fixtures. The agent example now uses MiniMax-M3 by default, with matching updates to environment examples, loader documentation, and test assertions to validate consistent usage.

Changes

MiniMax Model Version Upgrade

Layer / File(s)	Summary
Beginner Example Model Update examples/beginner/minimax_example.py	Module docstring and OpenAILike model identifier updated from MiniMax-M2.7 to MiniMax-M3.
Configuration Documentation Updates gateway/.env.example, gateway/src/config/loader.ts	Example comments for OPENROUTER_FALLBACK_MODELS updated to show minimax-m3 instead of minimax-m2.7.
Test Fixtures and Assertions gateway/tests/provider/openrouter-body-injection.test.ts, tests/unit/test_minimax_example.py	OpenRouter fallback test expects minimax-m3 in the models chain; unit tests now assert M3 usage and integration test payloads send MiniMax-M3 (except the separate highspeed variant which keeps MiniMax-M2.7-highspeed).

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Poem

🐰 A hop and a skip, M2.7 must go,
M3 arrives with a bright model glow,
Examples updated, tests sing in tune,
Config docs gleaming like a summer noon,
Consistency blooms across every file! 🌿

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically summarizes the main change: upgrading MiniMax model references from M2.7 to M3 across examples, documentation, and tests.
Description check	✅ Passed	The description comprehensively covers all required template sections: clear problem statement, why it matters, what changed, scope boundaries, change types, affected areas, user-visible changes, security impact, verification steps, backward compatibility, and risks with mitigations.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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