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/test/core/python-executor-streaming.test.ts

@@ -23,7 +23,7 @@ describe("executePythonWithKernel streaming", () => {
 		const largeOutput = "a".repeat(DEFAULT_MAX_BYTES + 128);
 		const kernel = new FakeKernel(
 			{ status: "ok", cancelled: false, timedOut: false, stdinRequested: false },
-			(options) => options?.onChunk?.(largeOutput),
+			options => options?.onChunk?.(largeOutput),
 		);
 
 		const result = await executePythonWithKernel(kernel, "print('hi')");
@@ -46,7 +46,7 @@ describe("executePythonWithKernel streaming", () => {
 	it("sanitizes ANSI and carriage returns", async () => {
 		const kernel = new FakeKernel(
 			{ status: "ok", cancelled: false, timedOut: false, stdinRequested: false },
-			(options) => options?.onChunk?.("\u001b[31mhello\r\n"),
+			options => options?.onChunk?.("\u001b[31mhello\r\n"),
 		);
 
 		const result = await executePythonWithKernel(kernel, "print('hello')");