Add natural-language component rerank service

[Mbeaulne]

Tophatting

No manual tophatting required. This PR only adds the rerank service and unit tests; UI wiring comes later.

What changed

Adds the service that asks an LLM to rerank existing component search results.

Important behavior:

• The LLM does not search the whole component library
• The local search index finds candidates first
• The LLM only reranks that small candidate list
• Unknown or invented component ids are ignored
• Scores are clamped to a safe range

Why

This makes natural-language search better without making the model responsible for retrieval.

Test plan

• Run pnpm exec vitest run src/services/naturalLanguageComponentSearchService.test.ts
• Run pnpm run typecheck --pretty false
• Confirm empty queries do not call fetch
• Confirm hallucinated ids are filtered out

[github-actions]

🎩 Preview

A preview build has been created at: 05-27-natural-language-rerank-service/94b985d

[Mbeaulne]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• Adds AI-generated component descriptions to Components V2 #2337
• Add AI rerank and detail actions to Components V2 #2323
• Add multi-source Components V2 search and filters #2322
• Add Components V2 route shell #2319
• Add component search support utilities #2318
• Extract shared component detail view #2317
• Add natural-language component rerank service #2321 👈 (View in Graphite)
• Add Agent Settings UI for AI search #2320
• Add BYOK component search settings hook #2316
• Add component search index service #2315
• master

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