feat: improve /plugin-dev:start command best practices compliance

Restructure command to follow Claude Code best practices and the
plugin's command-development skill guidelines:

- Add argument-hint to frontmatter for documenting $ARGUMENTS usage
- Reorder steps logically (arguments → context → question → route)
- Add explicit header field ("Create") for AskUserQuestion
- Make option structure explicit with label/description format
- Add explicit multiSelect: false for mutually exclusive choices
- Fix code fence language markers (``` → ```text)

Fixes #144

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: sjnims

plugins/plugin-dev/commands/start.md

@@ -1,5 +1,6 @@
 ---
 description: Start plugin development - choose your path
+argument-hint: [description]
 allowed-tools: AskUserQuestion, SlashCommand, TodoWrite
 model: sonnet
 disable-model-invocation: true
@@ -13,25 +14,22 @@ Welcome the user and help them choose the right path for their plugin developmen
 
 Present the user with a clear choice between two development paths, explain when each is appropriate, then route them to the correct workflow.
 
-## Step 1: Present Options with AskUserQuestion
+## Step 1: Handle Arguments
 
-Use the AskUserQuestion tool to ask the user which path they want to take. Present these options:
-
-**Question**: "What would you like to create?"
-
-**Options**:
+If the user provided arguments ($ARGUMENTS is not empty):
 
-1. **A plugin** (Recommended for most users)
-   - Description: "Create a single plugin with skills, commands, agents, hooks, or MCP integrations. Best for: building something new, adding functionality to Claude Code, or learning plugin development."
+- Analyze the arguments to see if intent is already clear
+- If arguments clearly indicate a plugin (e.g., "database migration tool"), suggest plugin path
+- If arguments clearly indicate a marketplace (e.g., "team collection", "distribute our plugins"), suggest marketplace path
+- Still ask for confirmation before routing
 
-2. **A marketplace**
-   - Description: "Create a collection to organize and distribute multiple plugins. Best for: teams sharing internal tools, publishing a curated set of plugins, or organizing existing plugins."
+**Initial request:** $ARGUMENTS
 
-## Step 2: Provide Context Before They Choose
+## Step 2: Provide Context
 
 Before presenting the question, briefly explain:
 
-```
+```text
 Welcome to the Plugin Development Toolkit!
 
 I'll help you get started. First, let me explain your options:
@@ -47,37 +45,49 @@ I'll help you get started. First, let me explain your options:
 - Choose this if you already have plugins to organize, or want to plan a collection upfront
 ```
 
-## Step 3: Route Based on Choice
+## Step 3: Ask User Question
+
+Use the AskUserQuestion tool to ask the user which path they want to take.
+
+**Header**: "Create"
+**Question**: "What would you like to create?"
+**multiSelect**: false
+
+**Options**:
+
+Option 1:
+
+- label: "A plugin (Recommended)"
+- description: "Create a single plugin with skills, commands, agents, hooks, or MCP integrations. Best for: building something new, adding functionality to Claude Code, or learning plugin development."
+
+Option 2:
+
+- label: "A marketplace"
+- description: "Create a collection to organize and distribute multiple plugins. Best for: teams sharing internal tools, publishing a curated set of plugins, or organizing existing plugins."
+
+## Step 4: Route Based on Choice
 
 After the user selects an option:
 
 **If they chose "A plugin"**:
+
 - Acknowledge their choice
 - Use the SlashCommand tool to invoke `/plugin-dev:create-plugin`
 - Pass through any context from $ARGUMENTS if provided
 
 **If they chose "A marketplace"**:
+
 - Acknowledge their choice
 - Use the SlashCommand tool to invoke `/plugin-dev:create-marketplace`
 - Pass through any context from $ARGUMENTS if provided
 
-## Step 4: Handle Arguments
-
-If the user provided arguments ($ARGUMENTS is not empty):
-- Analyze the arguments to see if intent is already clear
-- If arguments clearly indicate a plugin (e.g., "database migration tool"), suggest plugin path
-- If arguments clearly indicate a marketplace (e.g., "team collection", "distribute our plugins"), suggest marketplace path
-- Still ask for confirmation before routing
-
-**Initial request:** $ARGUMENTS
-
 ---
 
 ## Example Interactions
 
 ### Example 1: No arguments provided
 
-```
+```text
 User: /plugin-dev:start
 
 Claude: Welcome to the Plugin Development Toolkit!
@@ -99,7 +109,7 @@ I'll help you get started. First, let me explain your options:
 
 ### Example 2: Arguments suggest a plugin
 
-```
+```text
 User: /plugin-dev:start a code review assistant
 
 Claude: Welcome to the Plugin Development Toolkit!
@@ -116,7 +126,7 @@ Claude: Great! Let me start the plugin creation workflow...
 
 ### Example 3: Arguments suggest a marketplace
 
-```
+```text
 User: /plugin-dev:start organize our team's internal tools
 
 Claude: Welcome to the Plugin Development Toolkit!