feat(extraction): add Terraform/OpenTofu language support with module-boundary bridging (#83, #310, #648 — carries #706) (#1173)

* feat(extraction): add Terraform and OpenTofu language support

Index .tf, .tfvars, and .tofu files via the tree-sitter-terraform dialect
of HCL (vendored from @tree-sitter-grammars/tree-sitter-hcl, Apache-2.0).

Symbols extracted:
- resource / data  → class  (qualified "type.name" / "data.type.name")
- module           → module (qualified "module.name")
- variable         → variable (qualified "var.name")
- output           → variable (qualified "output.name")
- provider         → namespace
- locals           → constant per attribute (qualified "local.key")

References resolved cross-file:
- var.X, local.X, module.M[.out], data.T.N[.attr], <type>.<name>[.attr]
- built-ins skipped: each.*, count.*, self.*, path.*, terraform.workspace

The Terraform framework resolver disambiguates same-named candidates
across modules by preferring the one in the same directory as the
reference site, then by closest common-ancestor path, falling back to
the generic name matcher only when neither applies.

Validated on two Terraform monorepos (277 and 470 .tf files): indexing
runs in 1.3s and 2.4s respectively, query latency stays under 200ms,
and cross-module references resolve to the correct module 100% of the
time on inspected samples.

18 new extraction tests; full suite 1146/1148 green (2 pre-existing
flaky skips, 0 regressions).

* feat(terraform): bridge the module boundary and enforce directory scoping

Builds on #706. The module declaration was a dead end: module.M.out
resolved to the declaration and stopped, module inputs never reached the
child module's variables, and impact could not cross the boundary — on
real multi-module repos that breaks the core blast-radius question
("what breaks upstream if I change this module's variable/output").

- module blocks now wire across the boundary through :-scoped refs only
  the Terraform resolver understands: module.M:var.<input> → the child's
  variable node, module.M:output.<o> → the child's output node (emitted
  alongside the module.M declaration ref), and module.M:file → the local
  source directory's entry file (imports). Registry/git sources emit no
  file ref and resolve nothing — an out-of-repo module stays a visible
  boundary instead of a guess.
- .tfvars top-level assignments reference the variable they set, walking
  up to the nearest ancestor directory (envs/prod.tfvars → root vars).
- Resolution now enforces Terraform's real scoping: same-directory only
  (no cross-module fallback by common path prefix, no single-candidate
  anywhere-in-tree binding), and terraform refs never fall through to
  the generic name matcher — var.X can never legally bind outside its
  module directory, so the fallback could only add wrong edges.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* docs(terraform): README language table + changelog entry + agent-eval corpus

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: Javier Rodríguez Fernández <jfernandez@freepik.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -11,6 +11,7 @@ and adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ### New Features
 
+- CodeGraph now indexes **Terraform and OpenTofu** (`.tf`, `.tfvars`, `.tofu`) — resources, data sources, modules, variables, outputs, providers, and every `locals` attribute become symbols (e.g. `aws_s3_bucket.my_bucket`, `var.region`, `module.vpc`, `local.prefix`), and uses like `var.region`, `module.vpc.id`, `data.aws_caller_identity.current`, or `aws_s3_bucket.my.arn` are wired up cross-file, so search, callers, and impact queries return real results on infrastructure repos instead of nothing. Module calls are bridged across the module boundary: a `module` block's inputs link to the child module's variables, `module.vpc.vpc_id` reaches the child's `output "vpc_id"` definition, and the block's local `source` path links to the module's files — so "what breaks if I change this module's variable" reaches every caller instead of dead-ending at the declaration (registry and git sources are deliberately left as visible boundaries rather than guessed). `.tfvars` assignments link to the variables they set, including var-files kept in a subdirectory. Resolution follows Terraform's real per-directory scoping, so same-named variables across modules never cross-link and "what depends on `var.project_id`" in a multi-module repo never mixes in unrelated modules. Thanks @Javviviii2. (#83, #310, #648)
 - CodeGraph now indexes **CUDA** (`.cu`, `.cuh`) — kernels, device/host functions, structs, and classes become symbols, and the host→kernel call edge survives the `<<<grid, block>>>` launch syntax, so questions like "how does this call reach the GPU kernel?" trace across the CPU/GPU boundary instead of going dark at the launch site. Real-world launch styles all connect: templated launches (`my_kernel<Traits, 256><<<grid, block>>>(args)`), launches through a local function pointer (`auto kernel = &my_kernel<...>; ... kernel<<<grid, block>>>(args)` — each branch-assigned target linked), brace-initialized launch configs (`<<<dim3{1,1,1}, dim3{256,1,1}>>>`), and kernels defined through a name-in-first-argument macro (flash-attention's `DEFINE_FLASH_FORWARD_KERNEL(kernel_name, ...) { ... }` style), which now index under their real kernel names. CUDA that lives in plain `.h`/`.hpp` headers — where much real-world device code sits, launch-template headers included — is recognized by content and indexed the same way. Validated on llm.c, flash-attention, and NVIDIA CUTLASS. (#387, #648)
 - C++ symbols defined inside `namespace` blocks now carry the namespace in their qualified name (`flash::compute_attn`, C++17 `namespace a::b {` included), and namespace-qualified calls (`ns::fn(...)`) resolve to their definitions — previously such calls never linked at all, which hid much of the call graph in namespace-heavy C++ codebases from callers and impact analysis.
 - C++ calls that spell out template arguments (`fn<T, 256>(args)`) now link to the function they instantiate, the same normalization templated base classes already had.