Remove backend discovery from operator in dynamic mode

[yrobla]

In dynamic mode (outgoingAuth.source: discovered), the vMCP server owns backend discovery and reports status. The operator should only observe this status rather than discovering backends itself.

This change implements the responsibility shift described in the THV-2884 proposal. In static mode (outgoingAuth.source: inline), the operator continues to discover backends from MCPGroup as before.

Resolves #3004

[codecov]

Codecov Report

❌ Patch coverage is 68.75000% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 57.03%. Comparing base (51b37e3) to head (6f08a85).
⚠️ Report is 199 commits behind head on main.

Files with missing lines	Patch %	Lines
...perator/controllers/virtualmcpserver_controller.go	68.75%	8 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3248      +/-   ##
==========================================
+ Coverage   56.97%   57.03%   +0.06%     
==========================================
  Files         351      351              
  Lines       34962    34974      +12     
==========================================
+ Hits        19919    19948      +29     
+ Misses      13387    13365      -22     
- Partials     1656     1661       +5     

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[Copilot]

Pull request overview

This PR implements the removal of backend discovery from the operator in dynamic mode, as described in the THV-2884 proposal. In dynamic mode (outgoingAuth.source: discovered), the vMCP server owns backend discovery and reports status directly, while the operator only observes this status. In static mode (outgoingAuth.source: inline), the operator continues to discover backends from MCPGroup as before.

Changes:

• Added mode detection logic to differentiate between dynamic and static modes
• Refactored backend discovery to be mode-aware - skipped in dynamic mode, performed in static mode
• Added comprehensive tests covering both modes

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
docs/proposals/THV-2884-vmcp-k8s-aware-refactor.md	Updated proposal to reflect implementation status with checkmarks
cmd/thv-operator/controllers/virtualmcpserver_mode_test.go	Added comprehensive tests for mode detection and both dynamic/static mode behaviors
cmd/thv-operator/controllers/virtualmcpserver_controller.go	Added isDynamicMode helper and handleBackendDiscovery function to conditionally discover backends based on mode

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