feat(workflow): add Workflow SDK plugin to marketplace (#155)

Add Vercel's Workflow SDK plugin for building durable, reliable, and
observable TypeScript apps and AI agents. Includes marketplace entry,
release-please config, README documentation, and plugin directory with
skills installed via skills.sh.

Author: amondnet

.claude-plugin/marketplace.json

@@ -584,6 +584,14 @@
       "keywords": ["git-ai", "git", "ai", "code-tracking"],
       "tags": ["tooling", "git"],
       "source": "./plugins/git-ai"
+    },
+    {
+      "name": "workflow",
+      "description": "Workflow SDK: Build durable, reliable, and observable apps and AI Agents in TypeScript",
+      "category": "development",
+      "keywords": ["workflow", "durable", "vercel", "typescript", "ai-agents"],
+      "tags": ["framework", "workflow"],
+      "source": "./plugins/workflow"
     }
   ]
 }

README.md

@@ -292,6 +292,11 @@ A Git extension for tracking the AI-generated code in your repos.
 
 **Install:** `/plugin install git-ai@pleaseai` | **Source:** [plugins/git-ai](https://github.com/pleaseai/claude-code-plugins/tree/main/plugins/git-ai)
 
+#### Workflow
+Workflow SDK: Build durable, reliable, and observable apps and AI Agents in TypeScript.
+
+**Install:** `/plugin install workflow@pleaseai` | **Source:** [plugins/workflow](https://github.com/pleaseai/claude-code-plugins/tree/main/plugins/workflow)
+
 ## Quick Start
 
 The fastest way to get started — install the marketplace and let the plugin recommender auto-detect what you need:
@@ -377,6 +382,7 @@ Once the marketplace is added, install any plugin individually:
 /plugin install react-native@pleaseai
 /plugin install emulate@pleaseai
 /plugin install ask@pleaseai
+/plugin install workflow@pleaseai
 ```
 
 ## What Are Claude Code Plugins?