docs(claude-design): add SECURITY.md vulnerability disclosure policy

Repo had no SECURITY.md; adds one with a reachable contact address,
canonical repository URL, response process, and a version-support
table matching the actual 0.1.0 release line.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AX8SWgnoExWzZFKsxpg5N4

SECURITY.md

@@ -0,0 +1,33 @@
+# Security policy
+
+## Reporting a vulnerability
+
+Report privately to <security@fromaitochitta.com> - do not open a
+public issue.
+Canonical repository: https://git.fromaitochitta.com/open/claude-design
+
+Please include the affected version or commit, a minimal reproduction,
+and the impact you see. We acknowledge every report within 5 working
+days, agree a fix and disclosure timeline with the reporter, and aim to
+disclose within 90 days of the initial report.
+
+## Response process
+
+1. Acknowledge within 5 working days.
+2. Triage and confirm severity within 10 working days.
+3. Develop and test a fix.
+4. Publish an advisory and credit the reporter unless they prefer
+   to remain anonymous.
+
+## Supported versions
+
+| Version | Supported |
+| ------- | --------- |
+| 0.1.x   | Yes       |
+
+This is the only released line. Security fixes land on `main` and the
+next tagged release.
+
+## Advisories
+
+Security-relevant changes are noted in [CHANGELOG.md](CHANGELOG.md).