ge-hch.3.2: stable demo story + docs

[SorraTheOrc]

Summary

• Adds a canonical stable demo story at web/stories/demo.ink used as the fallback for M1.
• Updates docs/InkJS_README.md documenting the stable story and how to swap in generated stories.
• Adjusts E2E tests to use the stable story and added robust waiting logic to avoid flakiness.

Related bd issues

• ge-hch.3 (M1 — MVP)
• ge-hch.3.2 (Feature: Stable story integration)
• Delegation reference: bd comment id: 71

Files changed

• web/stories/demo.ink — stable demo story (100–400 lines)
• docs/InkJS_README.md — added "Stable demo story" section and CI validate command
• tests/demo.smoke.spec.ts — updated to wait/poll for story content/choices
• tests/demo.telemetry.spec.ts — updated to wait/poll for story content/choices
• .beads/issues.jsonl — bead state carried forward

Validation output
$(sed -n '1,200p' ./logs/validate-demo.out 2>/dev/null || cat /dev/null)

Test output (summary)
$(sed -n '1,200p' ./logs/test-summary.out 2>/dev/null || cat /dev/null)