feat: add commit-helper tool to optimize AI commit context

Replaces verbose git command invocations in commit commands with a smart
TypeScript helper that:
- Filters out lockfiles, binary files, and generated content from diffs
- Truncates large diffs intelligently by preserving complete file changes
- Provides structured summaries with file type distribution and change stats
- Shows previews of new files being added

Also adds Fish shell VSCode extension and enables Claude Code panel preference.

home/.config-source/cursor/settings.linux.json

@@ -337,5 +337,6 @@
   "svelte.enable-ts-plugin": true,
   "[svelte]": {
     "editor.defaultFormatter": "svelte.svelte-vscode"
-  }
+  },
+  "claudeCode.preferredLocation": "panel"
 }