Add telemetry instrumentation for optimizer

[aponcedeleonch]

Summary

• Wrap the optimizer factory with a telemetry decorator (telemetryOptimizer) that records OTel metrics and traces for FindTool and CallTool operations
• Metrics include request/error counters, duration histograms, result-set size, and token-savings percentages
• The decorator is applied in Server.Start when a TelemetryProvider is configured
• Add comprehensive table-driven unit tests covering success, error, and not-found scenarios

Test plan

• Unit tests pass (go test ./pkg/vmcp/server/... -count=1)
• go vet clean
• gofmt clean
• Deploy with OTel stack and verify metrics appear in Prometheus/Grafana

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 78.62595% with 28 lines in your changes missing coverage. Please review.
✅ Project coverage is 68.45%. Comparing base (d0102a2) to head (1e1ec2d).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/vmcp/server/telemetry.go	83.73%	10 Missing and 10 partials ⚠️
pkg/vmcp/server/server.go	0.00%	7 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3978      +/-   ##
==========================================
- Coverage   68.47%   68.45%   -0.02%     
==========================================
  Files         437      437              
  Lines       44419    44550     +131     
==========================================
+ Hits        30417    30498      +81     
- Misses      11636    11673      +37     
- Partials     2366     2379      +13     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[aponcedeleonch]

@jerm-dro will merge this. If you have any comment feel free to leave it and I will address it in a future PR