fix: align lint target discovery with files config

[fansenze]

Summary

This PR makes lint target selection files-driven and removes the old coupling where TypeScript Program membership could decide what gets linted.

• Resolve lint targets from config files (or rslint's default JS/JSX/TS extensions), explicit CLI/API file/dir inputs, global ignores, and rslint's existing .gitignore product behavior.
• Keep TypeScript Programs as execution containers only: selected files already covered by a tsconfig-backed Program reuse it; selected gap files get an AST-only fallback Program and no type-aware rules.
• Preserve type-check behavior: semantic diagnostics still come from tsconfig-backed Programs; fallback Programs are skipped for --type-check.
• Handle explicit files that miss files as selected 0-rule results, matching ESLint-style behavior, while suppressing syntax diagnostics when no config entry matches.
• Keep multi-config ownership nearest-config based for discovery, rule resolution, eslint-plugin routing, and Program target assignment.

Architecture Changes

• Added a shared programFileIndex so gap detection and target-to-Program binding use the same source-file index, including realpath aliases for symlink/path-canonicalization cases.
• Added an explicit source-path to config-path alias map so rules, globals, syntax diagnostics, and eslint-plugin routing are resolved against the lint target path even when the Program source path differs.
• Rebuild target bindings, type-info file sets, and config resolvers during --fix relint passes so relinting uses current Program state.
• Added FileConfigResolver to cache per-run per-file merged config and enabled rules, including nil misses.
• Added lintConfigResolver for CLI/API multi-config and single-config routing, reused by native lint, syntax diagnostic filtering, and eslint-plugin config resolution.
• Kept API full-memory linting intact across symlink/realpath aliases by expanding in-memory file overlays and preserving realpath lookup for virtual files backed by disk paths.
• Kept LSP aligned at the behavior level for file matching while leaving .gitignore parity as a separate follow-up.

Behavior Notes

• Missing files means the default lintable extension set, not arbitrary files.
• Empty/invalid files remains rejected by validation; JSON config migration still accepts legacy files: [] so it can drop unsupported empty fields while generating JS/TS config.
• Files included by files but outside tsconfig are linted without type-aware rules.
• CLI/API .gitignore behavior is preserved. LSP .gitignore parity is intentionally not changed in this PR and can be handled separately.

Real Repo Performance

Stage-prime results, 10 alternating old/new iterations, median wall time. The new build intentionally lints more files in both repos because missing files now uses the default lintable extension set.

Repo	Mode	Old	New	Delta	Files
rsbuild	plain	2620ms	3252ms	+24.1%	2027 -> 2052
rsbuild	type-check	3272ms	3755ms	+14.7%	2027 -> 2052
rspack	plain	2926ms	2740ms	-6.4%	475 -> 478
rspack	type-check	3124ms	2990ms	-4.3%	475 -> 478

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