fix(hashline): rejected line suffixes after snapshot tags

Rejected headers such as ¶src/file.ts#1A2B:42 as malformed headers instead of treating the whole tail as a hashless path and failing later in body parsing.

Added strict and apply_patch-recovery regression coverage for line-suffixed snapshot tags.

packages/hashline/src/input.ts

@@ -73,10 +73,11 @@ function tryParseRecoveryHeader(line: string, cwd?: string): RawSection | null {
 	}
 
 	// Same anti-junk rule as the strict tokenizer: a `#XXXX` token followed
-	// by whitespace+content inside the path body is a malformed header (e.g.
-	// stale-tag copy-paste like `src/a.ts#1A2B copied from read`), not a
-	// path with an embedded hex fragment.
-	if (new RegExp(`#[0-9A-Fa-f]{${HL_FILE_HASH_LENGTH}}\\s`).test(pathText)) return null;
+	// by whitespace+content or a line suffix inside the path body is a
+	// malformed header (e.g. stale-tag copy-paste like
+	// `src/a.ts#1A2B copied from read` or `src/a.ts#1A2B:42`), not a path
+	// with an embedded hex fragment.
+	if (new RegExp(`#[0-9A-Fa-f]{${HL_FILE_HASH_LENGTH}}(?:\\s|:)`).test(pathText)) return null;
 
 	const path = normalizeHashlinePath(pathText, cwd);
 	if (path.length === 0) return null;

packages/hashline/src/tokenizer.ts

@@ -334,10 +334,11 @@ function tryParseHeader(line: string): { path: string; fileHash?: string } | nul
 		}
 	}
 
-	// Reject stale-tag copy-paste such as `¶src/a.ts#1A2B copied from read`:
-	// a `#XXXX` token followed by whitespace+more content in the path body
-	// is a malformed header, not a path-with-embedded-hash. Surface the
-	// focused diagnostic instead of silently mis-routing the edit.
+	// Reject stale-tag copy-paste such as `¶src/a.ts#1A2B copied from read`
+	// and line-suffixed tags such as `¶src/a.ts#1A2B:42`: a `#XXXX`
+	// token followed by tag-tail junk in the path body is a malformed header,
+	// not a path-with-embedded-hash. Surface the focused diagnostic instead
+	// of silently mis-routing the edit.
 	for (let i = FILE_PREFIX_LENGTH; i + HL_FILE_HASH_LENGTH < pathEnd; i++) {
 		if (line.charCodeAt(i) !== CHAR_HASH) continue;
 		let allHex = true;
@@ -349,7 +350,9 @@ function tryParseHeader(line: string): { path: string; fileHash?: string } | nul
 		}
 		if (!allHex) continue;
 		const after = i + HL_FILE_HASH_LENGTH + 1;
-		if (after < pathEnd && isWhitespaceCode(line.charCodeAt(after))) return null;
+		if (after < pathEnd && (isWhitespaceCode(line.charCodeAt(after)) || line.charCodeAt(after) === CHAR_COLON)) {
+			return null;
+		}
 	}
 
 	if (pathEnd === FILE_PREFIX_LENGTH) return null;

packages/hashline/test/leniency.test.ts

@@ -28,12 +28,16 @@ describe("hashline section headers", () => {
 		expect(() => Patch.parse("¶src/a.ts#1A2B copied from read\nreplace 1..1:\n+after")).toThrow(
 			/Input header must be/,
 		);
+		expect(() => Patch.parse("¶src/a.ts#1A2B:812\nreplace 1..1:\n+after")).toThrow(/Input header must be/);
 	});
 
 	it("rejects trailing junk after a snapshot tag even with apply_patch noise", () => {
 		expect(() => Patch.parse("¶Update File: src/a.ts#1A2B copied from read\nreplace 1..1:\n+after")).toThrow(
 			/Input header must be/,
 		);
+		expect(() => Patch.parse("¶Update File: src/a.ts#1A2B:812\nreplace 1..1:\n+after")).toThrow(
+			/Input header must be/,
+		);
 	});
 });