fix(usage): merge case-insensitive trend model segments

[LceAn]

Summary

• merge trend tooltip model segments case-insensitively after trimming whitespace
• preserve the spelling of the variant with the highest usage while summing all variants
• add a regression test for GPT-5.5/gpt-5.5 and whitespace variants

Verification

• baseline TrendMonitor tests: 12 passed
• modified TrendMonitor tests: 13 passed
• dashboard lint, typecheck and production build: passed
• UI hardcode and architecture guardrails: passed

This PR is scoped to the Usage Trend display and is independent of the Windows stability work in #540.

Summary by CodeRabbit

• Bug Fixes
  • Improved trend breakdowns by combining model names that differ only by capitalization or extra spaces.
  • Excluded invalid or non-positive usage values from model totals.
  • Sorted model segments by usage and displayed the most-used spelling for each model.

[coderabbitai]

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ℹ️ Recent review info

⚙️ Run configuration

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Review profile: CHILL

Plan: Pro Plus

Run ID: 65e6e606-ec6d-460c-894f-5f4760721f80

📥 Commits

Reviewing files that changed from the base of the PR and between 58db7aa and cc6be18.

📒 Files selected for processing (2)

• dashboard/src/ui/dashboard/components/TrendMonitor.jsx
• dashboard/src/ui/dashboard/components/__tests__/TrendMonitor.test.jsx

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📝 Walkthrough

Walkthrough

The dashboard now merges model usage entries by trimmed, case-insensitive names. It filters invalid values, preserves the highest-usage display spelling, sorts totals, and uses the merged results for model bar segments. Tests cover normalization and aggregation.

Changes

Model Segment Normalization

Layer / File(s)	Summary
Merge and render normalized model segments dashboard/src/ui/dashboard/components/TrendMonitor.jsx, dashboard/src/ui/dashboard/components/__tests__/TrendMonitor.test.jsx	mergeModelSegments filters invalid values, merges normalized model names, preserves the highest-usage spelling, and sorts totals. getBarSegments uses the helper and retains the token-type fallback. Tests verify trimming, case-insensitive merging, and summed values.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: ⚪ Minimal · up to cc6be

This localized dashboard change merges equivalent model labels while preserving the highest-usage spelling and includes regression coverage; no actionable merge-blocking risk remains after normal checks and review.

Suggested reviewers: xiufengsun

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: merging usage trend model segments without case sensitivity.
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.

• Fix all pre-merge checks with AI

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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