feat: README rewrite, MCP section, vanilla/Vue demos + security hardening - #336

…n exceptions

- context.ts subscribe(): add try/catch around the sync subscriber callback
  to match the existing protection in subscribeAsync(); prevents a throwing
  subscriber from crashing the observer chain
- selection.ts: move destroy() before onCapture invocation and wrap the
  callback in try/catch so an exception in user code never leaves selection
  listeners dangling
- capture.ts: remove duplicate removeAffordance() call introduced during
  the previous commit; single call is sufficient and idempotent

…h try/catch

- capture.ts: guard onCapture, onCancel, and onSubmit callbacks so a
  consumer exception cannot propagate into internal pointer/key event
  handlers or leave the DOM in an inconsistent state
- selection.ts: guard onCancel so a throwing consumer cannot leave the
  cancel path half-executed; matches the onCapture fix from the previous commit

…wn exceptions

Wrap the user-supplied affordance render function in try/catch so an
exception does not interrupt the post-capture flow or leave internal
state inconsistent.

…la demo

README:
- New punchy headline: "Your LLM doesn't know what the user is looking at. Fix that in two lines."
- Lead with "What the AI receives" — shows actual promptContext output upfront
- Before/after comparison showing the problem (stale system prompt) vs the solution
- Prominent MCP section with 3-line setup and Claude Desktop config
- Better organized sections: capture modes, integrations table, framework quick starts
- Links to vanilla-chat example as zero-install demo

examples/vanilla-chat/index.html:
- Zero-install single-file demo that opens directly in any browser
- Full analytics dashboard (3 KPI cards, 4-row deal table) with data-askable
- Real-time "What the AI sees" panel showing live promptContext
- Mock AI chat that generates context-accurate responses from the actual data
- Copy context button, keyboard navigation, beautiful dark-mode design
- Loads @askable-ui/core from CDN — no build step

site/www/index.html:
- Updated page title and OG/Twitter meta tags with sharper copy
- Hero eyebrow: "Claude Desktop · Cursor · CopilotKit · any LLM" (was generic)
- Hero body paragraph: problem-first framing (no screenshots, no guessing)
- Nav: added MCP link, removed redundant Patterns/Integrations links
- Integrations section: added Claude Desktop and Cursor as MCP client cards (5 total)
- New MCP section with code examples, Claude Desktop config, and feature cards
- CTA: "Your AI. Your UI. Finally connected." + Live demo link added
- Footer: MCP guide and Live demo links added

Minimal Vue 3 + Vite demo showing the core askable-ui pattern:
- <Askable :meta="..."> keeps data-askable in sync with reactive props
- useAskable() composable returns promptContext ref that auto-updates
- Live "What the AI sees" panel showing the actual context string
- Mock AI chat demonstrating how specific and accurate responses become
  when the AI has real context (NRR/pipeline/deals with actual values)

Includes README with real-LLM wiring instructions for OpenAI/Anthropic.

… links

- vanilla-chat/README.md: explains zero-install approach, how CDN import
  works, and shows how to connect to a real LLM API (OpenAI/Anthropic)
- README.md: fix @askable/react → @askable-ui/react import typo
- README.md: expand Live links section with Vue, React Native, analytics
  dashboard, and vanilla examples with one-liner descriptions