style(deps): migrated from Prettier to Biome and updated formatting rules

- Removed Prettier configuration files (.prettierignore and .prettierrc) and migrated formatting to Biome.
- Updated Biome configuration from version 2.3.11 to 2.3.12 and changed arrowParentheses rule from 'always' to 'asNeeded'.
- Pinned @biomejs/biome dependency to exact version 2.3.12 in package.json and bun.lock.
- Applied consistent arrow function formatting across 489 files by removing unnecessary parentheses around single parameters.
- Removed blank lines after comment blocks and reorganized imports for consistency across the codebase.

packages/coding-agent/src/cli/file-processor.ts

@@ -1,7 +1,6 @@
 /**
  * Process @file CLI arguments into text content and image attachments
  */
-
 import * as fs from "node:fs/promises";
 import * as path from "node:path";
 import type { ImageContent } from "@oh-my-pi/pi-ai";