Add K8s manager infrastructure for vMCP dynamic backend discovery

[yrobla]

Implements controller-runtime manager wrapper for VirtualMCP servers running in Kubernetes with dynamic backend discovery mode. This provides the foundation for live backend updates without pod restarts.

Large PR Justification

This is an atomic PR that covers a single and isolated functionality. It also contains tests and can't be split.

Closes: #3000

[github-actions]

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## Large PR Justification

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[Copilot]

Pull request overview

This PR implements the Kubernetes manager infrastructure for VirtualMCP servers to support dynamic backend discovery. It introduces a controller-runtime manager wrapper that enables live backend updates without pod restarts when running in Kubernetes with outgoingAuth.source: discovered mode.

Key changes include:

• New K8s manager package wrapping controller-runtime for dynamic mode
• Readiness probe endpoint (/readyz) with cache sync gating for gradual rollout safety
• Integration of K8s manager lifecycle into the vMCP server command

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
pkg/vmcp/k8s/manager.go	New K8s manager wrapper that provides cache sync capabilities and lifecycle management for dynamic backend discovery
pkg/vmcp/server/server.go	Adds K8sManager config field and implements /readyz endpoint that gates readiness on cache sync status
pkg/vmcp/server/readiness_test.go	Unit tests for readiness endpoint covering static mode, dynamic mode with synced cache, and dynamic mode with unsynced cache
pkg/vmcp/k8s/manager_test.go	Unit tests for K8s manager covering validation, lifecycle, cache sync, and error scenarios
cmd/vmcp/app/commands.go	Integrates K8s manager creation and startup when running in dynamic discovery mode
test/e2e/thv-operator/virtualmcp/virtualmcp_lifecycle_test.go	E2E tests verifying K8s manager infrastructure, readiness probes, health endpoints, and status endpoint behavior

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[github-actions]

✅ Large PR justification has been provided. The size review has been dismissed and this PR can now proceed with normal review.

Large PR justification has been provided. Thank you!

[codecov]

Codecov Report

❌ Patch coverage is 58.62069% with 48 lines in your changes missing coverage. Please review.
✅ Project coverage is 57.20%. Comparing base (674e321) to head (c83366c).
⚠️ Report is 15 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/vmcp/app/commands.go	0.00%	23 Missing ⚠️
pkg/vmcp/k8s/manager.go	69.84%	16 Missing and 3 partials ⚠️
pkg/vmcp/server/server.go	80.00%	3 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3192      +/-   ##
==========================================
+ Coverage   57.16%   57.20%   +0.04%     
==========================================
  Files         343      347       +4     
  Lines       34384    34438      +54     
==========================================
+ Hits        19656    19701      +45     
- Misses      13091    13097       +6     
- Partials     1637     1640       +3     

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[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

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