feat: add metrics tracking http request

[phvalguima]

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[github-actions]

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Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

Scanned Files

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[Copilot]

Pull request overview

Adds OpenTelemetry metrics instrumentation to track counts and durations of outbound model (LLM) calls and MCP tool calls, improving observability of the responses server’s external dependencies.

Changes:

• Introduce a shared metrics module (src/lib/metrics.ts) defining counters and histograms for model calls and MCP tool calls.
• Record model call duration/count (tagged with status code + model name) in handleOneTurnStream.
• Record MCP tool call duration/count (tagged with status code + tool/server identifiers) in callMcpTool, and extend the OTEL mock in tests to support metrics.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
src/routes/responses/handleOneTurn.ts	Records model-call counter + duration around streamed LLM calls.
src/routes/responses/handleOneTurn.test.ts	Extends OpenTelemetry mock to include metrics.getMeter() and instruments.
src/mcp.ts	Records MCP tool-call counter + duration around MCP calls.
src/lib/metrics.ts	Defines OpenTelemetry meter instruments for model/MCP metrics.

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