fix(hooks): restore grep truncation by removing unused grep-output-truncator (#120)

The grep-output-truncator hook was never registered in index.ts, so grep
output was not being truncated since commit 03a4501 which removed grep/Grep
from tool-output-truncator's TRUNCATABLE_TOOLS list.

- Remove unused grep-output-truncator.ts
- Add "grep" and "Grep" back to tool-output-truncator's TRUNCATABLE_TOOLS

Co-authored-by: Claude <noreply@anthropic.com>

src/hooks/tool-output-truncator.ts

@@ -1,8 +1,9 @@
 import type { PluginInput } from "@opencode-ai/plugin"
 import { createDynamicTruncator } from "../shared/dynamic-truncator"
 
-// Note: "grep" and "Grep" are handled by dedicated grep-output-truncator.ts
 const TRUNCATABLE_TOOLS = [
+  "grep",
+  "Grep",
   "safe_grep",
   "glob",
   "Glob",