docs(skill): emphasize --from flag for branch-based work

[basnijholt]

Summary

• Added prominent guidance about using --from HEAD when spawning agents to review/test existing branches
• Added "Scenario 0: Code review of current branch" as the first example in the skill
• Includes comprehensive review criteria (DRY, KISS, YAGNI, no pointless wrappers, etc.)

Problem

When Claude uses the agent-cli-dev skill to spawn an agent for reviewing the current branch, it often forgets to pass --from HEAD. Without this flag, the new worktree starts from origin/main and doesn't contain the changes to review.

Changes

SKILL.md:

• Added "IMPORTANT: Using --from for branch-based work" section
• Clear examples showing --from HEAD for review tasks
• Explains when to use vs. not use --from

examples.md:

• Added "Scenario 0: Code review of current branch" as the first example
• Includes comprehensive review focus criteria
• Highlights the common mistake of forgetting --from

Test plan

• Verify skill files are in sync (pre-commit hook validates this)
• Test that Claude uses --from HEAD when asked to review current branch