Add ExportedTypeMap infrastructure to propagate resolved type bindings
across file boundaries. When file A exports `const user = getUser()`
(resolved to `User`), file B importing `user` now gets seeded with
`user → User`, enabling `user.save()` to produce CALLS edges.
Key components:
- `importedBindings` option on BuildTypeEnvOptions with scopeEnv seeding
AFTER walk() to respect first-writer-wins (local declarations win)
- `collectExportedBindings()` in call-processor using graph node
isExported flag (no SymbolDefinition changes needed)
- Inline Kahn's algorithm topological sort with level grouping for
parallel-safe file ordering and cycle detection
- Re-resolution pass in pipeline.ts: topological order, 3% skip
threshold, path validation, per-file export caps (500)
- 32 new tests: 11 topological sort, 6 seeding, 15 integration
(simple cross-file, re-export chain, circular imports)
All 3454 tests pass (32 net new, 0 regressions).
