fix(routing): filter internal Azure routing models from GitHub Copilot

[SebConejo]

Summary

• The Copilot API (api.githubcopilot.com/models) returns internal Azure routing entries (accounts/msft/routers/*) that are infrastructure-level load balancing endpoints, not user-facing chat models
• Added copilot entry to PROVIDER_NON_CHAT regex filter to exclude these at fetch time
• Applied filterNonChatModels() at cache-read time in getModelsForAgent() so previously-cached routing entries are also filtered out

Test plan

• Added unit test for filtering at fetch time (provider-model-fetcher.service.spec.ts)
• Added unit test for filtering at cache-read time (model-discovery.service.spec.ts)
• Connect GitHub Copilot as a provider and verify accounts/msft/routers/* models no longer appear in the model selection modal

---

Summary by cubic

Filters internal Azure routing models from GitHub Copilot so only real chat models appear. Filtering runs on fetch and on cache reads to remove accounts/msft/routers/* entries.

• Bug Fixes
  • Added copilot to PROVIDER_NON_CHAT to exclude router IDs.
  • Applied filterNonChatModels() to cached results in getModelsForAgent().
  • Added unit tests for both fetch-time and cache-time filtering.

^{Written for commit e638138. Summary will update on new commits.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.00%. Comparing base (028cbca) to head (e638138).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1596      +/-   ##
==========================================
+ Coverage   97.92%   98.00%   +0.08%     
==========================================
  Files         118      119       +1     
  Lines        8675     8936     +261     
  Branches     3265     3364      +99     
==========================================
+ Hits         8495     8758     +263     
+ Misses        178      176       -2     
  Partials        2        2              

Flag	Coverage Δ
frontend	98.00% <ø> (+0.08%)	⬆️
shared	100.00% <ø> (ø)

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[cubic-dev-ai]

No issues found across 5 files