fix(models): correct Grok effort tiers

[steebchen]

Problem

xAI accepts compatibility aliases in addition to each model's distinct reasoning controls. The Grok 4.6 catalogue exposed minimal even though xAI normalizes it to low, while Grok 4.5's intentionally narrower list was undocumented.

Changes

• expose Grok 4.5's distinct low, medium, and high controls
• expose Grok 4.6's distinct low, medium, high, and xhigh controls
• document why minimal, none, and max are not advertised

The existing xAI adapter already forwards reasoning_effort verbatim. Chat and Responses normalization already preserves reasoning text, summaries, reasoning-token usage, and cost details, so no adapter changes are needed.

Verification

Live xAI Chat Completions and native Responses probes verified both deployments:

• Grok 4.5: minimal normalizes to low; xAI documents xhigh as equivalent to high; none and max reject
• Grok 4.6: minimal normalizes to low; low, medium, high, and xhigh remain distinct; none and max reject
• Responses reflect the effective effort and include reasoning summaries
• Chat Completions return reasoning_content and nested reasoning-token usage
• usage totals and xAI cost ticks reconcile with catalogue pricing

Commands:

• focused model, usage, cost, and response-normalization tests: 186 passed
• TEST_MODELS=xai/grok-4-6 FULL_MODE=true pnpm test:e2e: 105 passed, 94 skipped
• pnpm format
• pnpm build

Summary by CodeRabbit

• Documentation
  • Updated reasoning-level options for Grok models.
  • Clarified that minimal and xhigh are aliases for existing reasoning tiers where applicable.
  • Updated supported options for grok-4-6 to include low, medium, high, and xhigh.

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ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between a0164d0 and 0226b20.

📒 Files selected for processing (1)

• packages/models/src/models/xai.ts

🚧 Files skipped from review as they are similar to previous changes (1)

• packages/models/src/models/xai.ts

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Walkthrough

The xAI model metadata documents reasoning-effort aliases for grok-4-5 and removes minimal from the exposed tiers for grok-4-6.

Changes

xAI reasoning effort support

Layer / File(s)	Summary
Reasoning-effort metadata updates packages/models/src/models/xai.ts	grok-4-5 documents minimal as low and xhigh as high. grok-4-6 exposes low, medium, high, and xhigh, without minimal.

Estimated code review effort: 1 (Trivial) | ~2 minutes

Merge Risk: ⚪ Minimal · up to 0226b

This PR updates Grok reasoning-effort options and forwards the newly supported tiers; no actionable merge-blocking risk remains after normal checks and review.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: correcting Grok reasoning effort tiers in the models package.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch verify-grok-4-5-reasoning

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