docs(talk-like-scarletkc): refine parallelism and contrasts

[scarletkc]

The existing guidance discouraged forced groups of three and contrasts that start with a negation. It did not clearly cover repeated sentence patterns of other lengths or an affirmative statement followed by an unnecessary negative contrast.

This change expands the existing rules to cover mechanical parallelism, symmetrical sentence pairs, and both orders of affirmative/negative contrast. It keeps natural lists, independently useful points, factual comparisons, and corrections available, with no fixed item count. SKILL.md points to the expanded guidance.

This PR contains only the parallelism and contrast follow-up.

Validation:

• python scripts/update_readme_skills.py --check — passed.
• Skill Creator quick_validate.py skills/talk-like-scarletkc — passed.
• git diff --check origin/main...HEAD — passed.
• Manually reviewed the wording and confirmed the published tree matches the validated local tree.
• No executable code changed; the unit suite was not rerun for this documentation-only follow-up.