CI build and CodeQL fail on existing AOT analyzer IL3050 diagnostics

[Widthdom]

Summary:
CI currently runs formatting and build paths with AOT/trim analyzers enabled. Existing IL3050 diagnostics across the codebase are promoted to errors before tests run, causing PR build and CodeQL jobs to fail even when the PR does not touch those call sites.

Evidence:

• PR Fix MCP index concurrency guard #2789 build ubuntu-latest net8.0 fails in Verify formatting while running dotnet format.
• PR Fix MCP index concurrency guard #2789 Analyze csharp fails during dotnet build CodeIndex.sln --configuration Release --no-restore.
• Representative errors include ActiveWorkspace.cs, McpServer.cs, QueryCommandRunner.cs, JsonEnvelopeWrapper.cs, GitHubIssueReporter.cs, and IndexCommandRunner.FullScan.cs using APIs that trigger IL3050 under AOT analysis.

Proposed direction:
Track the analyzer debt separately from ordinary issue-fix PRs. Either migrate the affected JSON paths to source-generation/AOT-safe APIs, or split CI so ordinary build/format checks do not fail on known AOT analyzer debt while a dedicated analyzer job reports it separately.

[Widthdom]

Work started on branch codex/fix-issue2796.

[Widthdom]

Verified on latest origin/main c9cd4ad via branch codex/fix-issue2796. The reported IL3050 CI failure path no longer reproduces: dotnet build CodeIndex.sln --configuration Release --no-restore succeeds with 0 warnings / 0 errors, and dotnet format CodeIndex.sln --verify-no-changes --no-restore exits 0. The existing mainline WarningsNotAsErrors/ILLinkTreatWarningsAsErrors configuration keeps the known analyzer diagnostics from failing ordinary build/format checks, so this issue is already fixed on main and no code-change PR is needed.