feat: v3.0.0 architecture overhaul

- Rename marketplace to lm-claude-plugins
- Move MCP servers to root with symlinks
- Add 6 PR tools to Gitea MCP (list_pull_requests, get_pull_request,
  get_pr_diff, get_pr_comments, create_pr_review, add_pr_comment)
- Add clarity-assist plugin (prompt optimization with ND accommodations)
- Add git-flow plugin (workflow automation)
- Add pr-review plugin (multi-agent review with confidence scoring)
- Centralize configuration docs
- Update all documentation for v3.0.0

BREAKING CHANGE: MCP server paths changed, marketplace renamed

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

plugins/pr-review/.mcp.json

@@ -0,0 +1,9 @@
+{
+  "mcpServers": {
+    "gitea": {
+      "command": "${CLAUDE_PLUGIN_ROOT}/mcp-servers/gitea/.venv/bin/python",
+      "args": ["-m", "mcp_server.server"],
+      "cwd": "${CLAUDE_PLUGIN_ROOT}/mcp-servers/gitea"
+    }
+  }
+}