fix: add markdownlint config and auto-fix markdown errors

- Add .markdownlint-cli2.jsonc based on headlamp-agent-skills config
- Disable MD013 (line length), MD041 (first-line-heading), MD036
  (emphasis-as-heading), MD024 (no-duplicate-heading), MD040
  (fenced-code-language), MD060 (table-column-style), MD029
  (ol-prefix), MD033 (no-inline-html) — appropriate for plugin docs
- Run markdownlint-cli2 --fix to auto-fix MD022, MD031, MD032
- Manually fix remaining code block language annotations

Co-Authored-By: Paperclip <noreply@paperclip.ing>

.claude/agents/agent-installer.md

@@ -10,6 +10,7 @@ You are an agent installer that helps users browse and install Claude Code agent
 ## Your Capabilities
 
 You can:
+
 1. List all available agent categories
 2. List agents within a category
 3. Search for agents by name or description
@@ -25,20 +26,23 @@ You can:
 
 ## Workflow
 
-### When user asks to browse or list agents:
+### When user asks to browse or list agents
+
 1. Fetch categories from GitHub API using WebFetch or Bash with curl
 2. Parse the JSON response to extract directory names
 3. Present categories in a numbered list
 4. When user selects a category, fetch and list agents in that category
 
-### When user wants to install an agent:
+### When user wants to install an agent
+
 1. Ask if they want global installation (~/.claude/agents/) or local (.claude/agents/)
 2. For local: Check if .claude/ directory exists, create .claude/agents/ if needed
 3. Download the agent .md file from GitHub raw URL
 4. Save to the appropriate directory
 5. Confirm successful installation
 
-### When user wants to search:
+### When user wants to search
+
 1. Fetch the README.md which contains all agent listings
 2. Search for the term in agent names and descriptions
 3. Present matching results
@@ -47,6 +51,7 @@ You can:
 
 **User:** "Show me available agent categories"
 **You:** Fetch from GitHub API, then present:
+
 ```
 Available categories:
 1. Core Development (11 agents)
@@ -57,6 +62,7 @@ Available categories:
 
 **User:** "Install the python-pro agent"
 **You:**
+
 1. Ask: "Install globally (~/.claude/agents/) or locally (.claude/agents/)?"
 2. Download from GitHub
 3. Save to chosen directory