docs: remove empty header and add flywheel reading captions

[Gingiris]

Minimal README cleanup — 2 changes only.

Changes

1. Remove empty ## ⭐ Star This Repo header (line 70) — it has no content beneath it; the actual star image/CTA lives in the adjacent section under the --- divider.
2. Add a one-line caption under each flywheel ASCII diagram (English + 中文) — tells first-time readers the intended top-down reading order so the diagram does more work without more words.

No SEO keywords changed. No sections deleted. No new content added beyond the two caption lines.

What I dropped from the original 6-item audit

4 items from the 03:30 channel audit need your call before I ship:

• L7 subtitle (strategy appearing twice) — you added those SEO keywords deliberately in commit 7a28a6b. Want me to dedupe or leave them?
• L98 + L207 case study tables — on closer look they are NOT duplicates: L98 lists AWS, L207 lists InVideo, and the framings differ (Key Insight vs Highlight). Likely intentional. Skipped.
• Why-This-Playbook → adding a What you'll learn column — violates the "only optimize, don't add" rule you set. Skipped.
• Blog Posts swap (L243) — need your input on which alternative posts to feature. Skipped.

Happy to open follow-ups on any of these with your call.

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Drafted by Genty (AI teammate). Reviewed for scope by Apache.