Add clangd navigation helper

docs/modernization/build-inventory.md

@@ -75,6 +75,8 @@ cmake --preset android-arm64
 powershell -ExecutionPolicy Bypass -File scripts\automation\platform-build.ps1 -Presets android-arm64
 powershell -ExecutionPolicy Bypass -File scripts\automation\package-smoke.ps1 -Preset windows-msvc-default -Configuration Debug
 cmake --fresh --preset windows-clangcl-asan
+python scripts/dev/clangd_nav.py symbols --file src/app_core/brush_ui.h --name execute_brush
+python scripts/dev/clangd_nav.py definition --file src/node_panel_brush.cpp --line 511 --column 39
 ```
 
 Known local toolchain state:
@@ -88,6 +90,14 @@ Known local toolchain state:
 - clang-cl: `C:\Program Files\LLVM\bin\clang-cl.exe` reports 18.1.8, but the
   selected VS 2026-preview STL expects Clang 20 or newer; see DEBT-0014 before
   treating `windows-clangcl-asan` as a passing sanitizer gate.
+- clangd/clang-query/clang-tidy are installed under `C:\Program Files\LLVM\bin`.
+  `scripts/dev/clangd_nav.py` provides agent-friendly symbol, definition,
+  declaration, implementation, reference, and hover lookup through clangd using
+  the current `compile_commands.json` from `windows-clangcl-asan`,
+  `android-arm64`, or a caller-provided build directory. It disables clangd
+  background indexing by default for quick current-translation-unit lookups; pass
+  `--background-index` when broader cross-file references are worth the extra
+  indexing work.
 - Android arm64 headless configure/build passes through root CMake and the
   `platform-build` automation wrapper for `pp_foundation`, `pp_assets`,
   `pp_paint`, `pp_document`, `pp_renderer_api`, `pp_renderer_gl`,