chore(ci): add MCP process CodeQL shard

Adds the focused MCP/process/tool-execution CodeQL security shard and documents it in CI docs.

Proof:
- Branch CodeQL security run https://github.com/openclaw/openclaw/actions/runs/25132942030 passed on 9d8ca2bae7.
- New mcp-process-tool-boundary analysis 1200250367 returned 0 results.
- Branch open CodeQL alerts: none.
- Workflow Sanity, Blacksmith Testbox, Blacksmith Build Artifacts Testbox, and OpenGrep PR Diff passed.

.github/workflows/codeql.yml

@@ -51,6 +51,11 @@ jobs:
             runs_on: blacksmith-4vcpu-ubuntu-2404
             timeout_minutes: 25
             config_file: ./.github/codeql/codeql-network-ssrf-boundary-critical-security.yml
+          - language: javascript-typescript
+            category: mcp-process-tool-boundary
+            runs_on: blacksmith-4vcpu-ubuntu-2404
+            timeout_minutes: 25
+            config_file: ./.github/codeql/codeql-mcp-process-tool-boundary-critical-security.yml
           - language: actions
             category: actions
             runs_on: blacksmith-8vcpu-ubuntu-2404