fix(hashline-edit): widen non-numeric prefix detection and remove duplicate try-catch

- Replace regex /^([A-Za-z_]+)#.../ with indexOf-based prefix check to catch
  line-ref#VK and line.ref#VK style inputs that were previously giving generic errors
- Extract parseLineRefWithHint helper to eliminate duplicated try-catch in
  validateLineRef and validateLineRefs
- Restore idempotency guard in appendWriteHashlineOutput using new output format
- Add tests for LINE42 extraction, line-ref hint, line.ref hint, and guard behavior

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/tools/hashline-edit/validation.test.ts

@@ -38,6 +38,32 @@ describe("parseLineRef", () => {
     expect(() => parseLineRef(ref)).toThrow(/not a line number/i)
   })
 
+  it("extracts valid line number from mixed prefix like LINE42 without throwing", () => {
+    //#given — normalizeLineRef extracts 42#VK from LINE42#VK
+    const ref = "LINE42#VK"
+
+    //#when / #then — should parse successfully as line 42
+    const result = parseLineRef(ref)
+    expect(result.line).toBe(42)
+    expect(result.hash).toBe("VK")
+  })
+
+  it("gives specific hint when hyphenated prefix like line-ref is used", () => {
+    //#given
+    const ref = "line-ref#VK"
+
+    //#when / #then
+    expect(() => parseLineRef(ref)).toThrow(/not a line number/i)
+  })
+
+  it("gives specific hint when prefix contains a period like line.ref", () => {
+    //#given
+    const ref = "line.ref#VK"
+
+    //#when / #then
+    expect(() => parseLineRef(ref)).toThrow(/not a line number/i)
+  })
+
   it("accepts refs copied with markers and trailing content", () => {
     //#given
     const ref = ">>> 42#VK|const value = 1"

src/tools/hashline-edit/validation.ts

@@ -38,12 +38,16 @@ export function parseLineRef(ref: string): LineRef {
       hash: match[2],
     }
   }
-  const nonNumericMatch = ref.trim().match(/^([A-Za-z_]+)#([ZPMQVRWSNKTXJBYH]{2})$/)
-  if (nonNumericMatch) {
-    throw new Error(
-      `Invalid line reference: "${ref}". "${nonNumericMatch[1]}" is not a line number. ` +
-        `Use the actual line number from the read output.`
-    )
+  const hashIdx = normalized.indexOf('#')
+  if (hashIdx > 0) {
+    const prefix = normalized.slice(0, hashIdx)
+    const suffix = normalized.slice(hashIdx + 1)
+    if (!/^\d+$/.test(prefix) && /^[ZPMQVRWSNKTXJBYH]{2}$/.test(suffix)) {
+      throw new Error(
+        `Invalid line reference: "${ref}". "${prefix}" is not a line number. ` +
+          `Use the actual line number from the read output.`
+      )
+    }
   }
   throw new Error(
     `Invalid line reference format: "${ref}". Expected format: "{line_number}#{hash_id}"`
@@ -51,17 +55,7 @@ export function parseLineRef(ref: string): LineRef {
 }
 
 export function validateLineRef(lines: string[], ref: string): void {
-  let parsed: LineRef
-  try {
-    parsed = parseLineRef(ref)
-  } catch (parseError) {
-    const hint = suggestLineForHash(ref, lines)
-    if (hint && parseError instanceof Error) {
-      throw new Error(`${parseError.message} ${hint}`)
-    }
-    throw parseError
-  }
-  const { line, hash } = parsed
+  const { line, hash } = parseLineRefWithHint(ref, lines)
 
   if (line < 1 || line > lines.length) {
     throw new Error(
@@ -145,22 +139,24 @@ function suggestLineForHash(ref: string, lines: string[]): string | null {
   }
   return null
 }
+function parseLineRefWithHint(ref: string, lines: string[]): LineRef {
+  try {
+    return parseLineRef(ref)
+  } catch (parseError) {
+    const hint = suggestLineForHash(ref, lines)
+    if (hint && parseError instanceof Error) {
+      throw new Error(`${parseError.message} ${hint}`)
+    }
+    throw parseError
+  }
+}
+
 
 export function validateLineRefs(lines: string[], refs: string[]): void {
   const mismatches: HashMismatch[] = []
 
   for (const ref of refs) {
-    let parsed: LineRef
-    try {
-      parsed = parseLineRef(ref)
-    } catch (parseError) {
-      const hint = suggestLineForHash(ref, lines)
-      if (hint && parseError instanceof Error) {
-        throw new Error(`${parseError.message} ${hint}`)
-      }
-      throw parseError
-    }
-    const { line, hash } = parsed
+    const { line, hash } = parseLineRefWithHint(ref, lines)
 
     if (line < 1 || line > lines.length) {
       throw new Error(`Line number ${line} out of bounds (file has ${lines.length} lines)`)