pkg: wire top-level CMake, clang-format/tidy, editorconfig

CMakeLists.txt: every lane's add_subdirectory() is now guarded by EXISTS
on that lane's CMakeLists.txt, so main configures no matter which lanes
have merged and a lane lights up its targets on merge with no edit here.
Dependencies are found at top level (gated on the consuming lane) so a
missing -dev package fails fast with a clear name. Warnings via
add_compile_options (survives the presets' CMAKE_CXX_FLAGS override);
VELOX_WERROR escape hatch. Verified end to end: `cmake --preset dev`
against a merged lane/core builds libveloxcore + tests, `ctest --preset
dev` green.

.clang-format: Google base, 4-space indent, 100 cols, right-aligned
pointers. .clang-tidy: small high-signal set (bugprone/performance/
concurrency/portability + selected modernize/readability). .editorconfig
mirrors both. .gitignore: build-*/ , CMakeUserPresets.json, profiling
and editor droppings.

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01HPPSGhiArbvQgwC2DNiURS

.clang-tidy

@@ -0,0 +1,45 @@
+# Velox clang-tidy config. Owned by lane PKG/QA. Runs on every PR (non-fatal advisory in
+# M0–M1, a required check from M2). Keep the enabled set small and high-signal; add checks
+# when they catch a real bug, not for completeness.
+---
+Checks: >
+  -*,
+  bugprone-*,
+  cert-err34-c,
+  cert-err58-cpp,
+  concurrency-*,
+  cppcoreguidelines-pro-type-member-init,
+  cppcoreguidelines-slicing,
+  cppcoreguidelines-virtual-class-destructor,
+  misc-definitions-in-headers,
+  misc-misplaced-const,
+  misc-unused-using-decls,
+  modernize-use-nullptr,
+  modernize-use-override,
+  modernize-use-using,
+  modernize-use-emplace,
+  modernize-loop-convert,
+  modernize-make-unique,
+  modernize-make-shared,
+  performance-*,
+  portability-*,
+  readability-container-size-empty,
+  readability-duplicate-include,
+  readability-misleading-indentation,
+  readability-redundant-*,
+  readability-simplify-boolean-expr,
+  readability-static-definition-in-anonymous-namespace,
+  -bugprone-easily-swappable-parameters,
+  -bugprone-narrowing-conversions,
+  -performance-avoid-endl,
+  -readability-redundant-access-specifiers
+
+WarningsAsErrors: ''
+HeaderFilterRegex: '(core|daemon|cli|nmhost|tools)/.*\.(hpp|h)$'
+FormatStyle: file
+
+CheckOptions:
+  - key: performance-move-const-arg.CheckTriviallyCopyableMove
+    value: 'false'
+  - key: bugprone-argument-comment.StrictMode
+    value: 'true'