fix: prepare v0.1.1-beta.1 scoped MCP follow-up

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Summary

• enforce attenuated credential organization scope in self-service request reads
• harden MCP gateway delegation and add the local gateway Compose overlays
• stage prereleases separately from stable channel promotion and finish OpenAPI metadata fixes
• join the HTTP MCP gateway test to the real API authority and persisted execution-token checks

Validation

• dotnet test tests/Helpdesk.Tests/Helpdesk.Tests.csproj --no-restore -v minimal
  • 1,193 passed, 6 skipped, 0 failed
• focused MCP host and persisted access pipeline: 24 passed
• recreated pre-fix F1 regression: failed as expected (Expected: 0, Actual: 1); fixed regression passes

Release

This prepares v0.1.1-beta.1 as a prerelease. It does not promote latest.