feat: add signed-audit-trails teaching plugin (third governance-category skill)

.claude-plugin/marketplace.json

@@ -13,7 +13,7 @@
     {
       "name": "documentation-standards",
       "source": "./plugins/documentation-standards",
-      "description": "HADS (Human-AI Document Standard) — semantic tagging convention for writing docs that work efficiently for both humans and AI models. Reduces token consumption by separating machine-critical facts from human context.",
+      "description": "HADS (Human-AI Document Standard) \u2014 semantic tagging convention for writing docs that work efficiently for both humans and AI models. Reduces token consumption by separating machine-critical facts from human context.",
       "version": "1.0.0",
       "author": {
         "name": "Niksa Barlovic",
@@ -900,7 +900,7 @@
       "description": "Binary reverse engineering, malware analysis, firmware security, and software protection research for authorized security research, CTF competitions, and defensive security",
       "version": "1.0.0",
       "author": {
-        "name": "Dávid Balatoni",
+        "name": "D\u00e1vid Balatoni",
         "url": "https://github.com/balcsida"
       },
       "homepage": "https://github.com/wshobson/agents",
@@ -909,7 +909,7 @@
     },
     {
       "name": "conductor",
-      "description": "Context-Driven Development plugin that transforms Claude Code into a project management tool with structured workflow: Context → Spec & Plan → Implement",
+      "description": "Context-Driven Development plugin that transforms Claude Code into a project management tool with structured workflow: Context \u2192 Spec & Plan \u2192 Implement",
       "version": "1.2.1",
       "author": {
         "name": "Seth Hobson",
@@ -1002,7 +1002,7 @@
         "url": "https://github.com/Anasss/qa-orchestra.git",
         "path": "."
       },
-      "description": "Multi-agent QA toolkit with 10 specialized agents covering the full QA lifecycle — orchestrator, environment-manager, functional-reviewer, test-scenario-designer, browser-validator, automation-writer, manual-validator, bug-reporter, release-analyzer, and smart-test-selector. Stack-agnostic, output-chained, designed around live validation via Chrome MCP.",
+      "description": "Multi-agent QA toolkit with 10 specialized agents covering the full QA lifecycle \u2014 orchestrator, environment-manager, functional-reviewer, test-scenario-designer, browser-validator, automation-writer, manual-validator, bug-reporter, release-analyzer, and smart-test-selector. Stack-agnostic, output-chained, designed around live validation via Chrome MCP.",
       "version": "1.0.0",
       "author": {
         "name": "Anass Rach",
@@ -1015,7 +1015,7 @@
     {
       "name": "protect-mcp",
       "source": "./plugins/protect-mcp",
-      "description": "Cedar policy enforcement + Ed25519 signed receipts for every Claude Code tool call. First cryptographic governance plugin — decisions are policy-gated before they run and every decision produces a tamper-evident receipt verifiable offline.",
+      "description": "Cedar policy enforcement + Ed25519 signed receipts for every Claude Code tool call. First cryptographic governance plugin \u2014 decisions are policy-gated before they run and every decision produces a tamper-evident receipt verifiable offline.",
       "version": "0.1.0",
       "author": {
         "name": "Tom Farley",
@@ -1025,7 +1025,39 @@
       "homepage": "https://veritasacta.com",
       "license": "MIT",
       "category": "governance",
-      "keywords": ["cedar", "receipts", "ed25519", "policy", "governance", "audit", "compliance"]
+      "keywords": [
+        "cedar",
+        "receipts",
+        "ed25519",
+        "policy",
+        "governance",
+        "audit",
+        "compliance"
+      ]
+    },
+    {
+      "name": "signed-audit-trails",
+      "source": "./plugins/signed-audit-trails",
+      "description": "Teaching skill: cookbook-style walkthrough for signed audit trails on every Claude Code tool call. Cedar policy, Ed25519 receipts, offline verification, CI/CD integration, SLSA composition. Pairs with the protect-mcp runtime plugin.",
+      "version": "0.1.0",
+      "author": {
+        "name": "Tom Farley",
+        "email": "tommy@scopeblind.com",
+        "url": "https://github.com/tomjwxf"
+      },
+      "homepage": "https://veritasacta.com",
+      "license": "MIT",
+      "category": "governance",
+      "keywords": [
+        "tutorial",
+        "skill",
+        "recipe",
+        "audit",
+        "governance",
+        "cedar",
+        "receipts",
+        "ed25519"
+      ]
     }
   ]
 }

plugins/signed-audit-trails/.claude-plugin/plugin.json

@@ -0,0 +1,10 @@
+{
+  "name": "signed-audit-trails",
+  "version": "0.1.0",
+  "description": "Teaching skill: signed audit trails for Claude Code tool calls. Cookbook-style walkthrough of Cedar-gated tool calls with Ed25519 receipts, offline verification, and CI/CD integration. Pairs with the protect-mcp plugin.",
+  "author": {
+    "name": "Tom Farley",
+    "email": "tommy@scopeblind.com"
+  },
+  "license": "MIT"
+}

plugins/signed-audit-trails/README.md

@@ -0,0 +1,57 @@
+# signed-audit-trails
+
+A teaching skill for setting up cryptographically signed audit trails on every
+Claude Code tool call. Cookbook-style walkthrough with runnable examples.
+
+## What this is
+
+A **skill** (not a runtime hook): a set of instructions and examples that
+explain the pattern end-to-end. Use this when you are figuring out whether
+receipts are the right fit for your project. Once you know they are, install
+the [`protect-mcp`](../protect-mcp/) plugin for the actual hooks.
+
+## When to use this plugin
+
+- **Learning** the pattern before committing to infrastructure
+- **Evaluating** whether signed audit trails fit your compliance need
+- **Teaching** team members the three-invariant cryptographic model
+  (JCS canonicalization + Ed25519 signatures + hash chains)
+- **Walking a client or auditor** through a live demonstration of tamper
+  detection
+
+For production use, the [`protect-mcp`](../protect-mcp/) plugin gives you the
+runtime hooks directly. This plugin is the skill file you invoke via
+`Skill` when you want the concept explained in-session.
+
+## What is inside
+
+```
+skills/signed-audit-trails-recipe/SKILL.md
+```
+
+A single skill file containing:
+
+- Step-by-step setup (Cedar policy, hook configuration, first receipt)
+- Live tamper detection walkthrough
+- Receipt format explanation (three invariants)
+- Cross-implementation interoperability table
+- CI/CD integration snippet (GitHub Actions)
+- Composition with SLSA provenance for agent-built software
+- Common pitfalls and references
+
+## Standards
+
+- **Ed25519** (RFC 8032) for receipt signatures
+- **JCS** (RFC 8785) for deterministic JSON canonicalization before signing
+- **Cedar** (AWS) for policy evaluation
+- **IETF draft** [draft-farley-acta-signed-receipts](https://datatracker.ietf.org/doc/draft-farley-acta-signed-receipts/)
+
+## Related plugins in this marketplace
+
+- [`protect-mcp`](../protect-mcp/) — the runtime hook implementation
+- [`review-agent-governance`](../review-agent-governance/) — require human
+  approval before review-surface actions; composes with protect-mcp
+
+## License
+
+MIT. Same as the adjacent governance-category plugins in this marketplace.