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/diff-utils.ts

@@ -9,7 +9,7 @@ export function toHashlineContent(content: string): string {
 	const hashlined = contentLines.map((line, i) => {
 		const lineNum = i + 1
 		const hash = computeLineHash(lineNum, line)
-		return `${lineNum}:${hash}|${line}`
+		return `${lineNum}#${hash}:${line}`
 	})
 	return hasTrailingNewline ? hashlined.join("\n") + "\n" : hashlined.join("\n")
 }