Organize Beta.1 documentation and polish the security roadmap

Reviewed source snapshot: 6f61f862391424d7175263c87e76380218513617
Default compact display and repository layout from the prior accepted local baseline are included.

.github/CONTRIBUTING.md

@@ -0,0 +1,3 @@
+# Contributing
+
+See the [contribution guide](../docs/development/CONTRIBUTING.md) and [development tests](../docs/development/TESTING.md). Keep diagnostics read-only; do not submit secrets or raw private reports.

.github/ISSUE_TEMPLATE/bug_report.md

@@ -16,4 +16,4 @@ labels: bug
 ## Steps and redacted evidence / 复现步骤与脱敏证据
 
 Do not attach passwords, keys, subscriptions, raw journals or full system inventories.
-Unknown/provider-limited results are not automatically bugs. For sensitive vulnerabilities use the private route in SECURITY.md.
+Unknown/provider-limited results are not automatically bugs. For sensitive vulnerabilities use the private route in [the security policy](../SECURITY.md).

.github/SECURITY.md

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+# Security policy
+
+Read the [security and privacy policy](../docs/security/SECURITY.md). Do not put credentials or raw reports in public Issues. Use private vulnerability reporting if enabled; otherwise request a private contact first.