Subscribe to MCP catalog notifications

[Aaronontheweb]

Summary

• Add modern MCP tool and prompt catalog notifications through subscriptions/listen.
• Use direct notifications for older servers that declare listChanged support.
• Keep the existing catalog poll as the compatibility and repair path.
• Tie each notification lease to one client generation.
• Coalesce notification bursts into one active refresh and one queued refresh.
• Keep usable connections after malformed acknowledgements or listener failures.
• Defer MCP resource behavior to Expose MCP resources through bounded list and read operations #1807.

Verification

• dotnet restore Netclaw.slnx
• dotnet test src/Netclaw.Daemon.Tests/Netclaw.Daemon.Tests.csproj --no-restore — 1,012 tests passed.
• ./scripts/smoke/run-smoke.sh mcp-setup — 5 checks passed.
• dotnet slopwatch analyze — 0 issues.
• pwsh ./scripts/Add-FileHeaders.ps1 -Verify
• openspec validate subscribe-mcp-catalog-notifications --strict
• Focused coverage reached 88.8% line coverage and 81.8% branch coverage for the notification lease.

The behavioral eval did not run because this shell lacks the required provider credentials.

Closes #1808