Update Agent Docs

Run at the end of every task that changes code. This is not optional.

Checklist

Files added or moved? → Update .github/memory/FILE_MAP.md (top-level area) and the matching .github/instructions/<area>.instructions.md (directory detail).

Memory file added, removed, renamed, or had its purpose change? → Update .github/memory/INDEX.md and any memory files that reference it.

Public API changed? → Update the matching .github/instructions/<area>.instructions.md (Compiler/IDE) and the owning project's PublicAPI.Unshipped.txt (RS0016 enforces this). API_MAP.md covers only repo-wide entry points.

New compiler error code, IDE diagnostic ID, or resource string added? → Reflect it in the matching .github/instructions/<area>.instructions.md; ensure ErrorCode.cs / IDEDiagnosticIds.cs / .resx (+ /t:UpdateXlf) are consistent.

New pattern established? → If repo-wide, add to .github/memory/CONVENTIONS.md; if layer-specific, add to the matching .github/instructions/<area>.instructions.md.

Surprising or undocumented behavior found? → Ask the user how they want it documented.

Changed test base classes, locations, or how to run a suite? → Repo-wide layout → .github/memory/TESTING_STRATEGY.md; layer-specific bases/conventions → .github/memory/testing/<area>.md.