feat(coding-agent): add read-only exploration tools (grep, find, ls) and --tools flag

Add grep, find, and ls tools for safe code exploration without modification risk.
These tools are available via the new --tools CLI flag.

- grep: Uses ripgrep (auto-downloaded) for fast regex searching. Respects .gitignore,
  supports glob filtering, context lines, and hidden files.
- find: Uses fd (auto-downloaded) for fast file finding. Respects .gitignore, supports
  glob patterns, and hidden files.
- ls: Lists directory contents with proper sorting and directory indicators.
- --tools flag: Specify available tools (e.g., --tools read,grep,find,ls for read-only mode)
- Dynamic system prompt adapts to selected tools with relevant guidelines

Closes #74

packages/coding-agent/src/tools/index.ts

@@ -1,11 +1,31 @@
 export { bashTool } from "./bash.js";
 export { editTool } from "./edit.js";
+export { findTool } from "./find.js";
+export { grepTool } from "./grep.js";
+export { lsTool } from "./ls.js";
 export { readTool } from "./read.js";
 export { writeTool } from "./write.js";
 
 import { bashTool } from "./bash.js";
 import { editTool } from "./edit.js";
+import { findTool } from "./find.js";
+import { grepTool } from "./grep.js";
+import { lsTool } from "./ls.js";
 import { readTool } from "./read.js";
 import { writeTool } from "./write.js";
 
+// Default tools for full access mode
 export const codingTools = [readTool, bashTool, editTool, writeTool];
+
+// All available tools (including read-only exploration tools)
+export const allTools = {
+	read: readTool,
+	bash: bashTool,
+	edit: editTool,
+	write: writeTool,
+	grep: grepTool,
+	find: findTool,
+	ls: lsTool,
+};
+
+export type ToolName = keyof typeof allTools;