feat(extraction): add CUDA language support (.cu/.cuh) (#387, #648) (#1172)

CUDA rides the C++ grammar via the Metal (#1121) dialect pattern:
blankCudaConstructs (offset-preserving) blanks execution-space specifiers
(__global__ family), __launch_bounds__(...), and <<<grid, block>>> launch
configs — which otherwise lex as shift operators and destroy the
host→kernel call edge entirely. Gated by .cu/.cuh extension OR by content
(looksLikeCudaSource), because much real CUDA lives in .h/.hpp headers:
cutlass launches most kernels from headers and flash-attention's launch
templates are .h. Safe by construction — no CUDA marker is valid C++
anywhere, and the launch blank is bounded + brace-balance-checked so a
stray <<< (committed merge-conflict markers) can never blank real code.

All real-world launch styles connect: plain, templated
(k<T, 256><<<...>>>), function-pointer (auto kernel = &fn<...>; with
branch reassignments each linked), dim3{...} brace-init configs, and
kernels defined through name-in-first-argument macros
(DEFINE_FLASH_FORWARD_KERNEL style — gtest TEST_F / PYBIND11_MODULE
shapes deliberately excluded by the two-lone-identifiers rule).

Two general C++ resolution wins the flow validation forced out:
- namespace blocks now prefix contained symbols' qualifiedNames
  (prefix-only — no namespace nodes, avoiding #1093-style crowd-out), so
  ns::fn(...) calls resolve; previously every namespace-qualified C++
  call was a permanently dead edge. cutlass: +30,864 edges (~10%), node
  count byte-identical.
- templated callees (fn<T, 256>(args)) strip template args at extraction
  (mirroring #1043 for base classes), so they match their definitions.

Validated on llm.c (165 host→kernel launch edges, was 0),
flash-attention (run_flash_fwd → flash_fwd_kernel → compute_attn traces
in one codegraph_explore call), and NVIDIA CUTLASS; fmt as the plain-C++
control (unchanged). A/B n=2/arm: Read/Grep displacement decisive on all
three repos (flash-attention Reads 29,13 → 5,2).

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

README.md

@@ -244,7 +244,7 @@ The reliable, universal payoff is **surgical context and speed**: CodeGraph coll
 | **Full-Text Search** | Find code by name instantly across your entire codebase, powered by FTS5 |
 | **Impact Analysis** | Trace callers, callees, and the full impact radius of any symbol before making changes |
 | **Always Fresh** | File watcher uses native OS events (FSEvents/inotify/ReadDirectoryChangesW) with debounced auto-sync — the graph stays current as you code, zero config |
-| **20+ Languages** | TypeScript, JavaScript, Python, Go, Rust, Java, C#, VB.NET, PHP, Ruby, C, C++, Objective-C, Metal, Swift, Kotlin, Scala, Dart, Lua, Luau, R, Erlang, CFML, COBOL, Solidity, Svelte, Vue, Astro, Liquid, Pascal/Delphi |
+| **20+ Languages** | TypeScript, JavaScript, Python, Go, Rust, Java, C#, VB.NET, PHP, Ruby, C, C++, CUDA, Objective-C, Metal, Swift, Kotlin, Scala, Dart, Lua, Luau, R, Erlang, CFML, COBOL, Solidity, Svelte, Vue, Astro, Liquid, Pascal/Delphi |
 | **Framework-aware Routes** | Recognizes web-framework routing files and links URL patterns to their handlers across 17 frameworks |
 | **Mixed iOS / React Native / Expo** | Closes cross-language flows that static parsing misses: Swift ↔ ObjC bridging, React Native legacy bridge + TurboModules + Fabric view components, native → JS event emitters, Expo Modules |
 | **100% Local** | No data leaves your machine. No API keys. No external services. SQLite database only |
@@ -703,6 +703,7 @@ is written):
 | C++ | `.cpp`, `.hpp`, `.cc` | Full support |
 | Objective-C | `.m`, `.mm`, `.h` | Partial support (classes, protocols, methods, `@property`, `#import`, message sends; `.mm` ObjC++ may parse incompletely) |
 | Metal | `.metal` | Full support (vertex/fragment/kernel functions, structs, type aliases, call edges — MSL parses as C++, with `[[attribute]]` annotations handled) |
+| CUDA | `.cu`, `.cuh` | Full support (kernels and device/host functions, structs, classes, host→kernel call edges through `<<<grid, block>>>` launch syntax — templated launches, function-pointer launches (`auto kernel = &fn<...>`), `dim3{...}` configs, and macro-defined kernels included; `__global__`/`__device__`/`__launch_bounds__` specifiers handled; CUDA in plain `.h`/`.hpp` headers recognized by content) |
 | Swift | `.swift` | Full support |
 | Kotlin | `.kt`, `.kts` | Full support |
 | Scala | `.scala`, `.sc` | Full support (classes, traits, methods, type aliases, Scala 3 enums) |