Simplify config, fix WarpGrep description, update thresholds

- Remove unnecessary env vars (API URL, timeouts) — hardcoded defaults
- Keep MORPH_COMPACT_CHAR_THRESHOLD (140k) and MORPH_COMPACT_RATIO (0.3)
  as user-tunable
- WarpGrep: "fast agentic search" not "semantic search"
- Add SWE-Bench Pro stats: WarpGrep alone +4% perf, -15% cost
- Compact threshold bumped from 80k to 140k chars