feat: add MiniMax M2.5 model and set as default

[roomote]

Related GitHub Issue

Closes: #11457

Description

This PR attempts to address Issue #11457 by adding the MiniMax M2.5 model to the provider and making it the new default.

Changes:

• Added MiniMax-M2.5 entry to minimaxModels in packages/types/src/providers/minimax.ts with specs from the issue:
  • 204,800 context window
  • 131,072 max output tokens
  • $0.30/M input, $1.20/M output
  • $0.375/M cache writes, $0.03/M cache reads
• Changed minimaxDefaultModelId from MiniMax-M2 to MiniMax-M2.5
• Updated MINIMAX_DEFAULT_MAX_TOKENS to 131,072 to match the new default model
• Updated hardcoded default model ID references in minimax.spec.ts

The existing M2, M2-Stable, and M2.1 models remain available for users who prefer them.

Feedback and guidance are welcome.

Test Procedure

• All 18 existing MiniMax tests pass after the changes
• Run: cd src && npx vitest run api/providers/__tests__/minimax.spec.ts
• Lint and type-check pass across the full monorepo (verified via pre-push hooks)

Pre-Submission Checklist

• Issue Linked: This PR is linked to an approved GitHub Issue (see "Related GitHub Issue" above).
• Scope: My changes are focused on the linked issue (one major feature/fix per PR).
• Self-Review: I have performed a thorough self-review of my code.
• Testing: New and/or updated tests have been added to cover my changes (if applicable).
• Documentation Impact: I have considered if my changes require documentation updates (see "Documentation Updates" section below).
• Contribution Guidelines: I have read and agree to the Contributor Guidelines.

Documentation Updates

• No documentation updates are required.

Additional Notes

Model specs were provided by @ataniii in the issue comments. The M2.5 model uses the same API endpoint (api.minimax.io) and Anthropic-compatible SDK path, so no handler changes were needed.

[roomote]

Rooviewer   See task

Review complete -- no issues found. The new MiniMax-M2.5 model entry correctly follows the existing pattern, specs match the issue, default model and constant updates are consistent, and all 18 tests pass.

_{Mention @roomote in a comment to request specific changes to this pull request or fix all unresolved issues.}