fix(review-pr): add verification checklist for multi-line suggestions

[worktrunk-bot]

Summary

• Replaces the vague "minimize the range" instruction for multi-line suggestions with a concrete 4-step verification checklist
• Addresses the root cause of [bot] suggestion diffs silently remove correct code (recurring) #1607: the bot constructs suggestion ranges that are wider than the replacement text, silently deleting correct code when applied

Root cause analysis

Investigated all three known cases:

1. pr-review: multi-line suggestion removes correct code along with the bug #1310 (PR Adds simplified install scripts #1309): start_line: 18, line: 22 — 5-line range replaced with fewer lines, deleting the git-wt fallback branch
2. pr-review: suggestion block eats code fence markers when target range includes backtick lines #1326 (PR fix(skill): add retry guard to prevent intra-run duplicate reviews #1322): start_line: 289, line: 291 — range included a closing ``` fence that GitHub consumed as the suggestion's own delimiter
3. fix: add confidence gates and evidence accumulation to review-reviewers #1598: start_line: 93, line: 127 — 35-line range replaced with a shorter rewrite, deleting the gh issue view code block

Common thread: the bot sets a line range covering more content than it intends to replace. The replacement text is shorter, so the surplus lines are silently deleted. The existing instruction ("minimize the range") didn't give the bot a way to verify correctness.

Fix

The new checklist requires the bot to:

1. Read the exact lines in the range before posting
2. Verify no silent deletions — every line must appear in the replacement or be intentionally removed
3. Cap range at ~10 lines — larger suggestions should be split or pushed as commits
4. Avoid spanning markdown fences — prevents delimiter collision

Test plan

• Review a PR with a multi-line suggestion opportunity and verify the bot follows the checklist
• Verify the bot splits or commits changes larger than ~10 lines instead of using a suggestion

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