Rust-native moduleResolution repo-local config extends/default handling

[jununfly]

This was generated by AI during triage.

Parent

• Roadmap plan: docs/plans/2026-06-22-rust-native-typescript-module-resolution-roadmap.md
• Config interpretation plan: docs/plans/2026-06-22-rust-native-config-interpretation-completion.md
• Roadmap node: 1-2-2. extends/default handling

What to build

Implement bounded repo-local TypeScript config extends handling for the Rust-native moduleResolution path. The completed slice should load repo-local JSON extends chains, merge only the moduleResolution-related compilerOptions consumed by Rust, preserve the correct path basis for path-bearing fields, and derive bounded defaults for missing options.

Supported extends shapes for this issue: relative paths, repo-local absolute paths, .json suffix completion, and directory completion to tsconfig.json. npm package extends is explicitly out of scope and should be reported with unsupported/no-go taxonomy rather than silently treated as loaded.

Merged fields are limited to moduleResolution, module, baseUrl, paths, rootDirs, allowJs, and resolveJsonModule.

Acceptance criteria

• Rust config loading supports repo-local JSON extends chains with cycle/depth protection and deterministic fallback/no-go diagnostics.
• Child config values override base config values for the resolver-owned compilerOptions subset.
• baseUrl, paths targets, and rootDirs keep the path basis of the config file where each field is declared.
• Missing moduleResolution is defaulted from module for the bounded supported modes, and the decision/profile surface can distinguish explicit vs defaulted values.
• Deterministic Rust tests cover positive extends, override behavior, path-basis behavior, defaulting, unsupported npm package extends, and cycle/depth protection.
• Default graph output remains bounded to repo-local moduleResolution behavior; no TypeScript compiler API runtime dependency is introduced.

Blocked by

None - can start immediately.

[jununfly]

This was generated by AI during triage.

Closing as implemented. Rust-native moduleResolution now supports bounded repo-local config extends handling for resolver-owned compilerOptions, including declaring-config path basis for path-bearing fields and defaulted moduleResolution mode reporting.

Evidence:

• cargo test -p zcodegraph-core
• closeout: docs/benchmarks/2026-06-22-config-interpretation-closeout.md