Persist restored session metadata to Redis in loadSession

[yrobla]

Summary

After a successful RestoreSession call, write the restored session's metadata back to Redis so per-backend session IDs stay current. Backends that ignore Mcp-Session-Id hints (e.g. SSE transports) assign a fresh ID on every restore; without this write the stale IDs persisted in Redis indefinitely.

With Redis kept consistent, revert checkSession's comparison from the narrowed MetadataKeyBackendIDs-only workaround (introduced in #4724) back to maps.Equal, restoring full cross-pod consistency detection for any metadata drift.

Fixes #4836

Type of change

• Bug fix
• New feature
• Refactoring (no behavior change)
• Dependency update
• Documentation
• Other (describe):

Test plan

• Unit tests (task test)
• E2E tests (task test-e2e)
• Linting (task lint-fix)
• Manual testing (describe below)

Changes

File	Change

Does this introduce a user-facing change?

Implementation plan

Approved implementation plan

Special notes for reviewers

[Copilot]

Pull request overview

This PR addresses cross-pod vMCP session consistency when sessions are restored from storage: after RestoreSession, it persists the restored session’s (potentially updated) metadata back into Redis/storage so per-backend session IDs don’t remain stale. With storage now kept current, checkSession reverts to full metadata comparison (maps.Equal) to detect any metadata drift across pods.

Changes:

• Persist restored session metadata back to storage in loadSession after a successful RestoreSession.
• Revert checkSession drift detection to full-map comparison via maps.Equal.
• Add unit tests covering (1) restored-metadata persistence and (2) eviction on stale per-backend session IDs.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
pkg/vmcp/server/sessionmanager/session_manager.go	Persist restored metadata to storage; restore full metadata drift detection in checkSession.
pkg/vmcp/server/sessionmanager/session_manager_test.go	Add tests ensuring restored metadata is written back and stale cached metadata triggers eviction.

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[codecov]

Codecov Report

❌ Patch coverage is 76.92308% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.15%. Comparing base (12f25e5) to head (4b9aabb).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/vmcp/server/sessionmanager/session_manager.go	76.92%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4842      +/-   ##
==========================================
+ Coverage   69.12%   69.15%   +0.02%     
==========================================
  Files         531      531              
  Lines       55183    55196      +13     
==========================================
+ Hits        38146    38170      +24     
+ Misses      14113    14103      -10     
+ Partials     2924     2923       -1     

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[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 5 comments.

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