feat: tsconfig path alias resolution for import tracking

[TonyStef]

Summary

• New src/resolve.ts module: ImportResolver that auto-detects the nearest tsconfig.json, parses compilerOptions.paths, and resolves aliased imports (e.g., @/lib/logger → src/lib/logger). Caches tsconfig lookups per directory for monorepo support.
• Removed startsWith('.') filters from ast.ts: All imports are now extracted by the parser. The resolver in core.ts decides what's local vs external — external packages return null and are skipped.
• Fixed re-export handling: handleExportStatement now skips ALL re-exports (not just relative ones). export { foo } from '@/utils' was previously added as a local symbol — now correctly treated as an import reference.
• Fixed latent path mismatch bug: canonicalizePath() normalizes all SymbolRef.file values consistently (strips .ts/.tsx/.js/.jsx extensions and /index suffixes). Previously, symbols_added stored src/helpers.ts while symbols_referenced stored src/helpers — these never matched.
• Backward compatibility: getRecentFootprints() canonicalizes stored paths on read, so old footprints (with extensions) match new canonical paths. Self-resolves as old entries expire.
• New --tsconfig CLI option and tsconfig-path action input for explicit override (auto-detected by default).
• New dependency: get-tsconfig (zero-dep, 7KB, CJS-compatible)

Test plan

• 56/56 tests pass (19 new resolver + 5 new AST + 32 existing)
• Typecheck clean
• Biome lint clean
• ncc bundle builds successfully (3786kB, up from 3756kB)
• Test on a real repo with @/ path aliases