test(hashline/payload-syntax): migrated to inline payload syntax

- Updated hashline parser tests to use inline payload syntax (e.g., `tagvpayload` instead of `tagv\npl(payload)`).
- Removed deprecated test cases for bare-blank-line and explicit-blank-payload syntax.

packages/coding-agent/test/edit-diff.test.ts

@@ -238,7 +238,7 @@ describe("computeHashlineDiff", () => {
 
 		// `1:` with the same line as payload is a true no-op: the edit
 		// fires through computeHashlineDiff but produces identical content.
-		const input = `¶${sourcePath}#${computeFileHash(`${line}\n`)}\n1:\n${line}\n`;
+		const input = `¶${sourcePath}#${computeFileHash(`${line}\n`)}\n1:${line}\n`;
 		const result = await computeHashlineDiff({ input }, tempDir);
 		expect("error" in result).toBe(true);
 		if ("error" in result) {