fix(coding-agent/core): dropped hashline sections without intermediate operations

- Updated hashline splitting to skip emitting a section when a path header has no following operations.
- Added a trimmed non-empty check so only sections with diff content are returned.
- Added tests for duplicate and trailing headers to ensure empty header-only chunks are silently dropped.

packages/coding-agent/src/hashline/input.ts

@@ -108,7 +108,8 @@ export function splitHashlineInputs(input: string, options: SplitHashlineOptions
 
 	const flush = () => {
 		if (currentPath.length === 0) return;
-		sections.push({ path: currentPath, diff: currentLines.join("\n") });
+		const hasOps = currentLines.some(rawLine => stripTrailingCarriageReturn(rawLine).trim().length > 0);
+		if (hasOps) sections.push({ path: currentPath, diff: currentLines.join("\n") });
 		currentLines = [];
 	};
 

packages/coding-agent/test/core/hashline.test.ts

@@ -422,6 +422,16 @@ describe("splitHashlineInput — @ headers", () => {
 			{ path: "b.ts", diff: `+ EOF\n${pl("b")}` },
 		]);
 	});
+
+	it("silently drops a duplicate header with no operations between them", () => {
+		const input = ["@@ src/foo.ts", "@@ src/foo.ts", `+ BOF`, pl("x")].join("\n");
+		expect(splitHashlineInputs(input)).toEqual([{ path: "src/foo.ts", diff: `+ BOF\n${pl("x")}` }]);
+	});
+
+	it("silently drops a trailing header with no operations", () => {
+		const input = ["@@ a.ts", "+ BOF", pl("a"), "@@ b.ts"].join("\n");
+		expect(splitHashlineInputs(input)).toEqual([{ path: "a.ts", diff: `+ BOF\n${pl("a")}` }]);
+	});
 });
 
 describe("hashline executor", () => {