Add sample guide, sample exports, and enriched build report

- examples/: sample guide store, .sfgz share archive, and exported
  output in all nine formats (JSON/MD/HTML×2/PDF/GIF/images/DOCX/PPTX)
- build_report.md now records packaging tool availability, fallback
  policy, offline guarantee, and verification entrypoints
- artifacts_manifest.json with sha256 checksums for packages + samples
- CHANGELOG entries for the welcome screen and renderer fixes

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -9,6 +9,22 @@ Initial release.
 
 ### Added
 
+- Welcome screen on launch: app title with three actions — New Capture
+  (creates a guide, opens the editor, and starts a capture session),
+  Existing Workspace (guide library), and Settings. The brand button
+  returns to the welcome screen from any view.
+
+### Fixed
+
+- Renderer scripts no longer collide in the shared global scope (the app
+  previously failed to boot with a blank window).
+- Focused-view toggle persists correctly (`step.focusedView.enabled`).
+- Annotation style edits no longer steal input focus on each keystroke.
+- Step list stays in sync after saves and undo/redo.
+- Escape deselects the active annotation instead of deleting it.
+
+### Added (initial feature set)
+
 - Guide library with folders, favorites, title + full-text search, and a
   quick-actions palette.
 - Capture engine: full-screen / active-window / region capture, delay,