examples: add transcript-server example with live speech transcription (#240)

* feat: add transcript-server example with live speech transcription

- New example: transcript-server with Web Speech API transcription
  - Start/stop recording with timer display
  - Live transcript with interim results
  - Send button to send transcript as ui/message to host
  - Copy button to copy full transcript
  - Sent messages marked with divider, greyed out
  - Experimental ui/update-model-context for live context updates
  - Transparent background, respects host theme

- Enable microphone and clipboard in basic-host sandbox iframes
  - Add allow="microphone; clipboard-write" to both outer and inner iframes
  - Required for Web Speech API, audio capture, and clipboard access

- Add alert popup in basic-host for ui/message from apps

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* style: format transcript-server files

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* test: add e2e test and golden for transcript-server

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* refactor: use @types/dom-speech-recognition instead of hand-rolled types

Removes ~50 lines of manually defined Web Speech API types in favor of
the community-maintained type package.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* fix: add newlines between transcript chunks when copying to clipboard

* refactor: unify transcript formatting with timestamps

- Add formatEntry() helper that includes [timestamp] prefix
- Add formatEntries() helper that joins entries with newlines
- Use same format for clipboard copy, send message, and model context
- DRY up duplicate code in send button handler

* fix: log model context update failures instead of silently swallowing

* fix: log model context updates for debugging

* refactor: pass permissions through loadSandboxProxy like csp

- Add permissions parameter to loadSandboxProxy in implementation.ts
- Build iframe allow attribute from permissions instead of hardcoding
- Update sandbox.ts to not hardcode allow attribute (set via notification)
- Add microphone + clipboardWrite permissions to transcript-server resource
- Update README to reflect permission configuration via resource _meta.ui

* fix(transcript-server): auto-expand instead of scroll

- Remove min-height: 100vh and overflow-y: auto
- Let content grow naturally with autoResize (default)
- Remove unnecessary scrollTop calls

* test: remove transcript timer mask (no longer dynamic)

* refactor: pass permissions through loadSandboxProxy like csp

* docs: document updateModelContext for transitional speech

* test: update e2e screenshots

* refactor: use app.updateModelContext() instead of raw request

* package-lock.json

* src/generated/schema.json

* test: update e2e screenshots from CI

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

examples/transcript-server/src/global.css

@@ -0,0 +1,12 @@
+* {
+  box-sizing: border-box;
+}
+
+html, body {
+  font-family: system-ui, -apple-system, sans-serif;
+  font-size: 1rem;
+  margin: 0;
+  padding: 0;
+  /* No height: 100% - body must grow with content for ResizeObserver to detect changes */
+  background: transparent;
+}