update-agent-docs

# Update Agent Docs Run at the end of every task that changes code. This is not optional. ## Checklist **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 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?** → 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`. **Any doc updated?** → No additional tracking needed. Git history tracks changes automatically. ## Documentation Quality Documentation must describe the repository's current state, not the history or mechanics of the change being made. Do not add guidance that only makes sense in the context of the current diff, mentions behavior removed by the task, or warns against a workaround that no longer exists. Before adding guidance, ask whether it would help a future contributor starting from a clean checkout; if not, leave it out. ## Creating New Doc Files If knowledge doesn't fit existing files: - Create a new file in `.github/memory/` with a descriptive name (e.g., `incremental-generators.md`, not `misc.md`). - Add YAML frontmatter with a `coverage` field describing what it covers. - Add a row to `.github/memory/INDEX.md`. You do not need permission to create new files in `.github/memory/`. This space is yours to evolve. ## Frontmatter Format New docs should have minimal frontmatter — only the `coverage` field: ```yaml --- coverage: Brief description of what this doc covers --- ``` Do NOT add `last_updated`, `updated_by`, `confidence`, or date fields. Git history provides this without creating merge conflicts.