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/tool-description.ts

@@ -5,7 +5,7 @@ WORKFLOW:
 2. Pick the smallest operation per logical mutation site.
 3. Submit one edit call per file with all related operations.
 4. If same file needs another call, re-read first.
-5. Use anchors as "LINE#ID" only (never include trailing ":content").
+5. Use anchors as "LINE#ID" only (never include trailing "|content").
 
 VALIDATION:
   Payload shape: { "filePath": string, "edits": [...], "delete"?: boolean, "rename"?: string }