Utils Explorer Welcome Message, Version Bump & Plugin README Overhaul (#462)

* Clarify plugin README install and usage steps

* feat(explorer): add welcome message to root endpoint and bump version to 0.4.0

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* docs(plugins): update all plugin READMEs for v0.4.0 with full platform list

- Rewrite main community guide with platform table (8 plugins), skills/agents
  inventory, Knowledge Explorer section, and per-platform install steps
- Add v0.4.0 badge and Knowledge Explorer section to VS Code, Cline,
  Continue, Windsurf, and OpenClaw READMEs
- Fix inconsistent tool count (12 → 17) across all READMEs
- Bump Python requirement from 3.8+ to 3.10+ across all plugins

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* docs: add PR description for utils → main

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* chore: remove PR_DESCRIPTION.md

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

plugins/.vscode-plugin/README.md

@@ -1,6 +1,6 @@
 # Semantica — VS Code Plugin
 
-Adds Semantica as an MCP server to VS Code (via GitHub Copilot Chat or any MCP-aware extension).
+> **v0.4.0** — Adds Semantica as an MCP server to VS Code (via GitHub Copilot Chat or any MCP-aware extension).
 
 ## MCP Server Setup
 
@@ -30,7 +30,19 @@ Or if using the VS Code MCP extension directly:
 }
 ```
 
+VS Code will discover all 17 Semantica skills and 3 agents automatically on connection.
+
+## Knowledge Explorer
+
+Launch the interactive graph dashboard from the terminal:
+
+```bash
+semantica-explorer --graph my_graph.json --port 8000
+```
+
+Open `http://localhost:5174` to explore nodes, edges, decisions, SPARQL, lineage, and more.
+
 ## Requirements
 
-- Python 3.8+
+- Python 3.10+
 - `pip install semantica`