feat: tsconfig compilerOptions.paths — aliased bare specifiers join the graph and follow moves

- index/tsconfig: JSONC sanitize (comments, trailing commas), baseUrl +
  star/exact path keys, first candidate only, longest-prefix wins; invalid
  or missing tsconfig silently means no aliases
- resolution pass: '.'-prefixed specifiers resolve relatively as before,
  bare ones go through the alias table and join the importer graph
- planner: remap keeps the alias shape while the moved file stays inside
  the mapped tree (morphological, since destinations do not exist yet),
  exact keys keep meaning only while still resolving to the target;
  otherwise the previous relative rewrite applies unchanged
- resolve_base extracted from resolve_module (shared extension/index
  guessing); MODULE_EXTS is the exact inverse for remapping
- e2e: @utils/str.ts -> @utils/text.ts inside alias, -> ./core/text.ts
  when leaving it, @cfg falls back to ./settings; check passes on aliases

src/core/index/tsconfig/tests.rs

@@ -0,0 +1,80 @@
+use super::{PathAliases, sanitize_jsonc};
+use crate::core::index::FileSet;
+use std::path::{Path, PathBuf};
+
+fn files(paths: &[&str]) -> FileSet {
+    let mut set = FileSet::default();
+    for p in paths {
+        set.add(PathBuf::from(p));
+    }
+    set
+}
+
+fn aliases(json: &str) -> PathAliases {
+    PathAliases::parse(&sanitize_jsonc(json))
+}
+
+const TSCONFIG: &str = r#"{
+  // comment with a brace }
+  "compilerOptions": {
+"baseUrl": "./",
+"paths": {
+  "@/*": ["src/*"],
+  "@utils/*": ["src/shared/utils/*"],
+  "@cfg": ["src/config.ts"],
+},
+  },
+  "include": ["src/**/*"],
+}"#;
+
+#[test]
+fn jsonc_comments_and_trailing_commas_parse() {
+    let a = aliases(TSCONFIG);
+    assert_eq!(a.entries.len(), 3);
+}
+
+#[test]
+fn resolution_prefers_the_longest_matching_prefix() {
+    let set = files(&[
+        "src/shared/utils/str.ts",
+        "src/utils/str.ts",
+        "src/config.ts",
+    ]);
+    let a = aliases(TSCONFIG);
+    assert_eq!(
+        a.resolve("@utils/str", &set).as_deref(),
+        Some(Path::new("src/shared/utils/str.ts"))
+    );
+    assert_eq!(
+        a.resolve("@/utils/str", &set).as_deref(),
+        Some(Path::new("src/utils/str.ts"))
+    );
+    assert_eq!(
+        a.resolve("@cfg", &set).as_deref(),
+        Some(Path::new("src/config.ts"))
+    );
+    assert_eq!(a.resolve("react", &set), None);
+}
+
+#[test]
+fn remap_keeps_alias_shape_inside_and_falls_back_outside() {
+    let set = files(&["src/utils/str.ts", "src/deep/str.ts", "src/config.ts"]);
+    let a = aliases(r#"{"compilerOptions": {"paths": {"@u/*": ["src/utils/*"]}}}"#);
+    // Destination need not exist yet: the plan runs before the move.
+    assert_eq!(
+        a.remap("@u/str", Path::new("src/utils/other.ts"), &set)
+            .as_deref(),
+        Some("@u/other")
+    );
+    // Target outside the alias tree: caller must fall back to relative.
+    assert!(a.remap("@u/str", Path::new("lib/other.ts"), &set).is_none());
+}
+
+#[test]
+fn string_contents_survive_sanitizing() {
+    let json = r#"{"url": "http://x.com//y", "a": [1, 2,], /* c */ "b": "/*n*/"}"#;
+    let cleaned = sanitize_jsonc(json);
+    let value: serde_json::Value = serde_json::from_str(&cleaned).unwrap();
+    assert_eq!(value["url"], "http://x.com//y");
+    assert_eq!(value["b"], "/*n*/");
+}