feat(callgraph): C/C++ explicit type inference engines

[shivasurya]

Summary

Adds the explicit type-tracking foundation for C/C++ call-graph resolution.

• graph/callgraph/resolution/c_types.go — CTypeInferenceEngine, CFunctionScope, CVariableBinding. Tracks return types and per-function variable scopes drawn directly from source declarations.
• graph/callgraph/resolution/cpp_types.go — CppTypeInferenceEngine embeds the C engine and adds class method / class field indices, plus auto handling.

TypeInfo contract

Source	Confidence	Used for
declaration	1.0	Explicit types from source — return types, variable decls, class members
unresolved_auto	0.0	C++ auto x = ... placeholders awaiting Phase 2 deduction

Design notes

• Embedding: CppTypeInferenceEngine embeds CTypeInferenceEngine by value, so every C-engine method (ExtractReturnType, GetScope, GetVariable, etc.) is callable on the C++ engine. The embedded Registry field aliases the C++ registry's CModuleRegistry facet so updates propagate.
• Reassignment: each variable name keeps a slice of bindings; GetVariable returns the latest. GetAllBindings exposes the history for future flow analysis.
• auto detection: exact equality on \"auto\". Modifiers like auto* and auto& are concrete types and keep full confidence — they survive the override branch and route through the C engine unchanged.
• Void returns: explicitly dropped at registration so void functions never pollute downstream lookups (which gate on GetReturnType != nil).
• Thread safety: four sync.RWMutex instances guard Scopes, ReturnTypes, ClassMethods, ClassFields. Snapshot accessors (GetAllReturnTypes, GetAllScopes) return defensive copies.
• Lazy scope creation: ExtractVariableType creates the scope on first use; callers do not need to call AddScope before the first variable.

Test plan

• go build ./...
• go test ./... — full suite green (25 packages)
• go test -race ./graph/callgraph/resolution/... — clean
• go vet ./...
• golangci-lint run ./graph/callgraph/resolution/ — 0 issues
• Coverage on changed lines: c_types.go 100%, cpp_types.go 100%
• Spec test cases covered: NewC*Engine, ExtractReturnType (success + void), AddReturnType, ExtractVariableType (basic + reassignment), GetScope miss, AddScope, concurrent access (-race), embedded methods, RegisterClassMethod (success + void/empty drops + redeclaration), RegisterClassField (success + empty drops), auto zero-confidence, auto*/auto& exact-match, complex C types (pointer/const/struct), complex C++ types (templates / refs / nested templates).

Stacked on

shiva/cpp-module-registry (#672)

[safedep]

SafeDep Report Summary

No dependency changes detected. Nothing to scan.

View complete scan results →

_{This report is generated by SafeDep Github App}

[github-actions]

Code Pathfinder Security Scan

No security issues detected.

Metric	Value
Files Scanned	4
Rules	205

---

_{Powered by Code Pathfinder}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.28%. Comparing base (b9a6ef5) to head (47d63d3).

Additional details and impacted files

@@                      Coverage Diff                      @@
##           shiva/cpp-module-registry     #673      +/-   ##
=============================================================
+ Coverage                      85.18%   85.28%   +0.09%     
=============================================================
  Files                            180      182       +2     
  Lines                          26237    26399     +162     
=============================================================
+ Hits                           22351    22515     +164     
+ Misses                          3024     3023       -1     
+ Partials                         862      861       -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.