[bitbound]

Summary

Adds three Windows-only MCP tools so agents can activate UI Automation controls through their patterns without moving the real pointer. Pattern activation is exact and works while the window is covered, complementing the pixel tools; click stays the fallback for custom-drawn surfaces. Closes #1.

Approach

• list_elements(window) resolves the window through the existing WindowsWindowService, walks the UIA control view with max_depth / max_elements bounds and optional control_type / name filters, and caches matched elements under session-scoped ids (e1, e2, ...). Each line reports control type, name, automation id, bounding rect in physical px, and supported patterns.
• perform_action drives invoke / toggle / expand / collapse / set_value / select / scroll_into_view against a cached id. get_element_state reads Name/Value/Toggle/RangeValue/ExpandCollapse/selection without a screenshot.
• Hand-written COM interop (Uia/UiaInterop.cs) in the repo's existing raw P/Invoke style. No new NuGet dependency. FlaUI 5.x is net10.0-windows-only while this project targets plain net10.0, so it was ruled out.
• Registered in the existing OperatingSystem.IsWindows() block in Program.cs. README and the agent skill document the new tools, including a "try UIA before pixels" tip.

Reviewer notes

• COM interface member order is UIAutomationClient.h vtable order. Uncalled slots are padded placeholders and trailing slots are omitted (safe prefix rule); BB0001 is suppressed in that file only.
• Ids never reuse numbers. Re-listing a window drops its previous entries, and stale elements map COM failures to a loud "re-run list_elements" message.
• All UIA calls run on thread-pool threads (already MTA, as UIA requires) behind a 10 s timeout that abandons rather than aborts a hung provider. Flagged in code comments as a first-iteration trade-off.

Verification

• dotnet build clean, 0 warnings; all 117 tests pass. 21 new unit tests cover the pure seams: cache id numbering and window replacement, action parsing/validation, and output formatting.
• Live smoke through the packaged build (dnx -y over stdio JSON-RPC) against real Notepad windows: filtered and unfiltered tree walk with truncation reporting, set_value verified by reading the value back, scroll_into_view, and every error path (unknown id, unknown action, missing value, unknown window).

Fixes: #1