Each vault demo gets its own page

• Live demos is now a nav group of four: the side-by-side overview plus a dedicated page per vault — demo-risk-graph-explorer.html, demo-agentic-browser-isolation.html, demo-risk-mandate-field.html — mirroring how sgit.ai gives each published vault its own page.
• Each page carries the auto-opening embed front and centre, the published read key, four things to try in your first five minutes, a walkthrough of why the vault is shaped the way it is (the seven-views spine and fact-derived disagreement for the explorer; the fractal register and the no-deny door for browser isolation; grant-vs-mandate applied to ourselves — an app using an LLM whose key it cannot read — for the field demo), and cross-links to the other two.
• One template, three pages. The build now supports shared-source pages: a PAGE_CONFIG entry can declare src (a sibling directory it shares) plus template, per-page tokens for title/description, and a vault id injected as page data. The three pages are one template and one component set rendered three times — a bug fixed once is fixed everywhere.
• The overview keeps all three embeds and now links each card to its full walkthrough.
• Smoke: 19 groups — per-page titles substituted, one embed per vault page, walkthrough and cross-links present, and the nav group derived from the manifest as usual.