refactor: rename plugins/ to extensions/ for statusline

The statusline is a standalone utility, not a plugin in the
traditional sense. "Extensions" better describes tools that extend
Claude Code's behavior without fitting the skill/agent/MCP categories.

Author: yepzdk

.claude-plugin/marketplace.json

@@ -15,7 +15,7 @@
     {
       "name": "itkdev-statusline",
       "description": "Claude Code statusline with git branch, plan progress, and context window usage",
-      "source": "./plugins/itkdev-statusline"
+      "source": "./extensions/itkdev-statusline"
     }
   ]
 }

CHANGELOG.md

@@ -9,7 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
-- `itkdev-statusline` plugin with context window usage, git branch, and plan progress display
+- `itkdev-statusline` extension with context window usage, git branch, and plan progress display
 
 ## [0.4.0] - 2026-02-20
 

README.md

@@ -18,6 +18,8 @@ itkdev-claude-plugins/
 ├── agents/                     # Agents (flat .md files)
 │   ├── itkdev-code-review.md
 │   └── itkdev-issue-workflow.md
+├── extensions/                 # Extensions (standalone tools)
+│   └── itkdev-statusline/
 ├── skills/                     # Skills (subdirectories with SKILL.md)
 │   ├── itkdev-adr/
 │   ├── itkdev-documentation/
@@ -75,6 +77,12 @@ GitHub workflow guidelines for the ITK Dev team. Automatically activates when wo
 
 Autonomous GitHub issue workflow. Works through GitHub issues with minimal user interaction — handling development, testing, review, and merge — only pausing when user review or merge approval is required.
 
+## Included Extensions
+
+### itkdev-statusline
+
+Claude Code statusline displaying git branch, plan/task progress, and context window usage. Install with `/setup-statusline` after adding the marketplace. See [extensions/itkdev-statusline/README.md](extensions/itkdev-statusline/README.md) for details.
+
 ## Included Agents
 
 ### itkdev-code-review
@@ -168,6 +176,23 @@ description: When this skill should be activated automatically.
 Your skill instructions here...
 ```
 
+### Adding Extensions
+
+Create a subdirectory in `extensions/` with its own `.claude-plugin/plugin.json` and any commands or scripts:
+
+```
+extensions/
+└── your-extension-name/
+    ├── .claude-plugin/
+    │   └── plugin.json
+    ├── bin/
+    │   └── your-script.sh
+    └── commands/
+        └── setup-your-extension.md
+```
+
+Extensions are standalone tools (statuslines, utilities, setup scripts) that don't fit the skill/agent/MCP categories but benefit from marketplace distribution.
+
 ### Adding Agents
 
 Create a flat `.md` file in `agents/` with YAML frontmatter: