fix: byte-sliceable L3 statement nodes

src/dataflow/extract.ts

@@ -81,7 +81,16 @@ function emitNode(id: number, kind: GraphNode["kind"], ast: Node | null, build:
   const target = ast ?? build.fn; // ENTRY/EXIT carry the whole callable's span
   const s = build.sf.getLineAndColumnAtPos(target.getStart());
   const e = build.sf.getLineAndColumnAtPos(target.getEnd());
-  return { id, kind, start_line: s.line, start_column: s.column, end_line: e.line, end_column: e.column };
+  return {
+    id,
+    kind,
+    start_line: s.line,
+    start_column: s.column,
+    end_line: e.line,
+    end_column: e.column,
+    start_offset: target.getStart(),
+    end_offset: target.getEnd(),
+  };
 }
 
 function hasRestParam(build: FunctionCfgBuild): boolean {

src/schema/graphs.ts

@@ -34,6 +34,9 @@ export interface GraphNode {
   start_column: number;
   end_line: number;
   end_column: number;
+  /** UTF-16 char offsets into the owning module's `source` (same convention as L1 `span.bytes`). */
+  start_offset: number;
+  end_offset: number;
 }
 
 // ----------------------------------------------------------------------------------------------

test/schema-v2.test.ts

@@ -344,6 +344,16 @@ describe("schema v2 — L3 intraprocedural dataflow", () => {
   test("no dangling endpoints at L3", () => {
     expect(danglingCount(dfL3)).toBe(0);
   });
+
+  test("a sampled L3 statement node is source-sliceable (span.bytes reproduces its text)", () => {
+    const mod = dfL3.application.symbol_table["src/flow.ts"];
+    const classify = mod.functions.classify as V2Callable;
+    const stmt = classify.body["4:3"];
+    expect(stmt?.kind).toBe("statement");
+    const [s, e] = (stmt as { span: { bytes: [number, number] } }).span.bytes;
+    expect(e).toBeGreaterThan(s);
+    expect(mod.source.slice(s, e)).toBe('let label = "none";');
+  });
 });
 
 describe("schema v2 — L4 interprocedural SDG", () => {