v1.8.2: Encourage the LLM to cut when rewriting

Improvement

LLMs skew additive — when asked to shorten, they'll rephrase or add before they delete, and tend to keep an existing line just because it's already there. The over-budget rewrite guidance listed what to drop but never gave the model permission to drop things on its own judgment.

This release adds that permission where it matters:

• Over-budget rewrite prompt: "Be willing to DELETE. When unsure a line earns its place, cut it — don't keep it just because it's already there. A dropped low-value line costs nothing; a kept one costs budget every read."
• Writing guide: "When unsure, CUT."

Both flow through the shared guidance to every over-budget entry point — direct rewrite, update_ai_readme, the compress_ai_readme handoff, and validate_ai_readmes "needs rewriting" tier — i.e. exactly when a file is too long and the model needs to trim it.

Prompt text only; no behavior or API changes.