Rename ralph-wiggum plugin to ralph-loop per legal guidance (#142)

- Rename plugin from "ralph-wiggum" to "ralph-loop" to avoid trademark concerns
- Update all internal references to use "Ralph Loop" as the prominent name
- Keep explanatory text noting it "implements the Ralph Wiggum technique" (allowed)
- Rename plugin directory from plugins/ralph-wiggum to plugins/ralph-loop
- Update marketplace.json with new plugin name and source path
- Update plugin-dev documentation references

This change follows legal's recommendation to replace "Wiggum" with "Loop"
in the plugin name while still explaining the technique origin.

Slack thread: https://anthropic.slack.com/archives/C09KU300P7F/p1767741142753959

Co-authored-by: Claude <noreply@anthropic.com>

plugins/ralph-loop/.claude-plugin/plugin.json

@@ -0,0 +1,8 @@
+{
+  "name": "ralph-loop",
+  "description": "Continuous self-referential AI loops for interactive iterative development, implementing the Ralph Wiggum technique. Run Claude in a while-true loop with the same prompt until task completion.",
+  "author": {
+    "name": "Anthropic",
+    "email": "support@anthropic.com"
+  }
+}