docs: add missing frontmatter and title fields

- Add full frontmatter (title, summary, read_when) to 4 files that
  had none: auth-credential-semantics.md, kilo-gateway-integration.md,
  CONTRIBUTING-THREAT-MODEL.md, THREAT-MODEL-ATLAS.md
- Add missing title field to 3 provider docs: kilocode.md, litellm.md,
  together.md

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/security/CONTRIBUTING-THREAT-MODEL.md

@@ -1,3 +1,11 @@
+---
+title: "Contributing to the Threat Model"
+summary: "How to contribute to the OpenClaw threat model"
+read_when:
+  - You want to contribute security findings or threat scenarios
+  - Reviewing or updating the threat model
+---
+
 # Contributing to the OpenClaw Threat Model
 
 Thanks for helping make OpenClaw more secure. This threat model is a living document and we welcome contributions from anyone - you don't need to be a security expert.

docs/security/THREAT-MODEL-ATLAS.md

@@ -1,3 +1,11 @@
+---
+title: "Threat Model (MITRE ATLAS)"
+summary: "OpenClaw threat model mapped to the MITRE ATLAS framework"
+read_when:
+  - Reviewing security posture or threat scenarios
+  - Working on security features or audit responses
+---
+
 # OpenClaw Threat Model v1.0
 
 ## MITRE ATLAS Framework