fix: sync all version files to 0.30.2 and add CI check

The 0.30.2 bump was done manually and missed several files:
- .claude-plugin/plugin.json (was 0.30.0)
- .claude-plugin/marketplace.json (was 0.30.0)
- npm-package/package.json (was 0.30.1)
- integrations/beads-mcp/pyproject.toml (was 0.30.1)
- integrations/beads-mcp/src/beads_mcp/__init__.py (was 0.30.1)

Added scripts/check-versions.sh and CI job to prevent this in future.
Always use scripts/bump-version.sh for version bumps.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

integrations/beads-mcp/src/beads_mcp/__init__.py

@@ -4,4 +4,4 @@ This package provides an MCP (Model Context Protocol) server that exposes
 beads (bd) issue tracker functionality to MCP Clients.
 """
 
-__version__ = "0.30.1"
+__version__ = "0.30.2"