Fix flaky vMCP health endpoint tests

[JAORMX]

Summary

Fixes intermittent test failures in pkg/vmcp/server/health_test.go that were occurring in CI due to port conflicts.

Problem

The health endpoint tests were flaky because all parallel test instances tried to bind to the default port 4483, causing "address already in use" errors when running with -parallel flag.

Solution

1. Added Ready() channel to vMCP server (pkg/vmcp/server/server.go):

   • Added ready chan struct{} field to signal when server is ready to accept connections
   • Exposed via Ready() <-chan struct{} method
   • Channel is closed after listener is created in Start()

2. Used existing networking.FindAvailable() utility (pkg/vmcp/server/health_test.go):

   • Each test now gets a unique random port (range 10000-65535)
   • Eliminates port conflicts between parallel tests

3. Improved test synchronization:

   • Tests wait for srv.Ready() channel instead of arbitrary sleeps
   • Added error channel to catch and report startup failures early
   • Better error messages including actual server address

Test Plan

Verified with stress testing:

go test -v ./pkg/vmcp/server -run TestHealthEndpoint -count=20 -parallel=4

All 60 tests (20 iterations × 3 subtests) passed reliably in ~0.26s.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 54.43%. Comparing base (4ef4a16) to head (bf81090).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2415   +/-   ##
=======================================
  Coverage   54.43%   54.43%           
=======================================
  Files         265      265           
  Lines       25590    25599    +9     
=======================================
+ Hits        13931    13936    +5     
- Misses      10338    10340    +2     
- Partials     1321     1323    +2     

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