[docs] 1-minute YouTube demo video uploaded

[jdev-02]

Owner: P3 (capture) + P4 (script). Coordinator: Jon.
Acceptance: Sun 1100-1200 window — capture, edit, upload, link.

Recording infrastructure is ready (PR #87, #89, #76, #78). 7 component clips
live in docs/demo-clips/. The 1-minute pitch cut still needs to:

• Sun 1100 — record 1-minute pitch from PRD §12 5-minute structure.
• Sun 1145 — edit (likely just titlecard + score-bar).
• Sun 1200 — upload to YouTube unlisted.
• Sun 1200 — paste URL into hackathon submission form.
• Sun 1200 — add link to README §Demo + docs/SUBMISSION_NOTES.md.

Source: TASKS.md #25.