refactor(hashline-edit): redesign hashline format with CID-based hashing

Breaking Changes:
- Change hashline format from 'lineNum:hex|content' to 'lineNum#CID:content'
- Replace hex-based hashing (00-ff) with CID-based hashing (ZPMQVRWSNKTXJBYH nibbles)
- Simplify constants: HASH_DICT → NIBBLE_STR + HASHLINE_DICT
- Update patterns: HASHLINE_PATTERN → HASHLINE_REF_PATTERN + HASHLINE_OUTPUT_PATTERN

Benefits:
- More compact and memorable CID identifiers
- Better alignment with LSP line reference format (lineNum#ID)
- Improved error messages and diff metadata clarity
- Remove unused toHashlineContent from diff-enhancer hook

Updates:
- Refactor hash-computation for CID generation
- Update all diff-utils to use new format
- Update hook to use raw content instead of hashline format
- Update tests to match new expectations

🤖 Generated with assistance of [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

src/tools/hashline-edit/hash-computation.ts

@@ -1,16 +1,16 @@
-import { HASH_DICT } from "./constants"
+import { HASHLINE_DICT } from "./constants"
 
 export function computeLineHash(lineNumber: number, content: string): string {
+  void lineNumber
   const stripped = content.replace(/\s+/g, "")
-  const hashInput = `${lineNumber}:${stripped}`
-  const hash = Bun.hash.xxHash32(hashInput)
+  const hash = Bun.hash.xxHash32(stripped)
   const index = hash % 256
-  return HASH_DICT[index]
+  return HASHLINE_DICT[index]
 }
 
 export function formatHashLine(lineNumber: number, content: string): string {
   const hash = computeLineHash(lineNumber, content)
-  return `${lineNumber}:${hash}|${content}`
+  return `${lineNumber}#${hash}:${content}`
 }
 
 export function formatHashLines(content: string): string {