feat(init): add grep and glob local-op handlers

Add two new local-op types that let the server search project files
without reading them all:

- grep: regex search across files with optional glob filter, batched
  (multiple patterns in one round-trip), capped at 100 matches per
  search with 2000-char line truncation

- glob: find files by pattern, batched (multiple patterns in one
  round-trip), capped at 100 results

Three-tier fallback chain (following gemini-cli's approach):
1. ripgrep (rg) — fastest, binary-safe, .gitignore-aware
2. git grep / git ls-files — fast, available on nearly every dev machine
3. Node.js fs walk — always works, no dependencies

Counterpart server-side schemas in cli-init-api PR #80.

Made-with: Cursor

Author: betegon