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>

examples/sample-exports/markdown/reset-a-password-in-admin-portal.md

@@ -0,0 +1,56 @@
+# Reset a password in Admin Portal
+
+Offline sample guide showing capture, annotations, rich text, and exports.
+
+## Contents
+
+- [1. Open Admin Portal users](#step-1)
+- [2. Enable the reset policy](#step-2)
+  - [2.1. Confirm permission prompt](#step-2-1)
+- [3. Review the confirmation](#step-3)
+
+<a id="step-1"></a>
+
+## 1. Open Admin Portal users
+
+Open the users list and select the target account.
+
+![Step 1](steps-reset-a-password-in-admin-portal/001-open-admin-portal-users.png)
+
+> **Note: Tip**
+> Use the search box to avoid scrolling.
+
+<a id="step-2"></a>
+
+## 2. Enable the reset policy
+
+Make sure the policy is active before continuing.
+
+![Step 2](steps-reset-a-password-in-admin-portal/002-enable-the-reset-policy.png)
+
+```bash
+stepforge --capture --window --delay 300
+```
+
+<a id="step-2-1"></a>
+
+### 2.1. Confirm permission prompt
+
+Only administrators can complete this step.
+
+> **Warning: Access**
+> Admin rights required.
+
+<a id="step-3"></a>
+
+## 3. Review the confirmation
+
+Confirm the summary and close the modal.
+
+![Step 3](steps-reset-a-password-in-admin-portal/004-review-the-confirmation.png)
+
+| Field | Value |
+| --- | --- |
+| Title | Admin Portal |
+| Owner | Support |
+