fix(workspace): honor project(":name").projectDir relocation in settings.gradle

[Hessesian]

Summary

Fixes #326. A project that groups its modules under a parent directory in settings.gradle.kts via project(":name").projectDir = file("modules/name") had that module's source roots silently lost: settings_subprojects derived every module's directory purely from the include(...) string, never reading a projectDir relocation. detect_build_layout_source_paths then probed a directory that doesn't exist, read_dir failed, and the module's src/*/kotlin roots never got discovered — explaining the reporter's exact symptom (highlighting fine, navigation/find-references mostly broken, since highlighting is per-file and source-root-independent while cross-file resolution depends on correct source-root scoping).

• New parse_project_dir_overrides parses project(":name").projectDir = ... lines (Kotlin DSL file(...), Groovy new File(...), or a bare string — all just one quoted name + one quoted path per line), robust to same-line comments/interpolation (degrades to a harmless no-crash mismap, never a panic).
• settings_subprojects now maps each include-derived directory through the override when one exists; both existing callers (detect_build_layout_source_paths, detect_android_r_class_jars) get the fix for free, untouched.
• Zero behavior change for a project with no projectDir overrides (confirmed: empty override map → unwrap_or(dir) is a no-op for every entry).

Test plan

• settings_gradle_relocated_module_dir_is_discovered — end-to-end, reproduces the reporter's exact settings.gradle.kts shape; confirmed genuinely RED without the fix (temporarily reverted, reran, real panic; restored)
• Unit tests for parse_project_dir_overrides: Kotlin DSL, Groovy new File(...), bare string, two negative/decoy cases (a project(...) reference with no .projectDir at all; a project(...).projectDir-shaped line that configures something else)
• settings_subprojects_passes_through_a_non_relocated_module_unchanged — mixed relocated + non-relocated project, exercises the real unwrap_or(dir) fallback end-to-end
• cargo test (2020 passed), cargo clippy --all-targets -- -D warnings (clean), cargo fmt (clean)
• Reviewed (traced token-matching heuristic against contrived self-reference/comment/interpolation shapes, confirmed key-construction parity with parse_include_calls for nested modules, confirmed cross-platform path-join correctness for the Windows separator case) — two test-coverage gaps found and fixed before this push

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https://claude.ai/code/session_01L7ZonwYUh94VsuQphiHykF