refactor(hashline): change content separator from colon to pipe

Change LINE#HASH:content format to LINE#HASH|content across the entire
codebase. The pipe separator is more visually distinct and avoids
conflicts with TypeScript colons in code content.

15 files updated: implementation, prompts, tests, and READMEs.

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

@@ -13,7 +13,7 @@ export function computeLineHash(lineNumber: number, content: string): string {
 
 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 {