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/hashline-edit-diff.ts

@@ -14,16 +14,16 @@ export function generateHashlineDiff(oldContent: string, newContent: string, fil
     const hash = computeLineHash(lineNum, newLine)
 
     if (i >= oldLines.length) {
-      diff += `+ ${lineNum}#${hash}:${newLine}\n`
+      diff += `+ ${lineNum}#${hash}|${newLine}\n`
       continue
     }
     if (i >= newLines.length) {
-      diff += `- ${lineNum}#  :${oldLine}\n`
+      diff += `- ${lineNum}#  |${oldLine}\n`
       continue
     }
     if (oldLine !== newLine) {
-      diff += `- ${lineNum}#  :${oldLine}\n`
-      diff += `+ ${lineNum}#${hash}:${newLine}\n`
+      diff += `- ${lineNum}#  |${oldLine}\n`
+      diff += `+ ${lineNum}#${hash}|${newLine}\n`
     }
   }