fix: Sync all component versions to 0.9.2

Fixes version inconsistencies across the project. All components now at 0.9.2:

Updated:
- .claude-plugin/plugin.json: 0.9.0 → 0.9.2
- .claude-plugin/marketplace.json: 0.9.0 → 0.9.2
- integrations/beads-mcp/pyproject.toml: 1.0.0 → 0.9.2
- README.md: v0.9.0 → v0.9.2
- PLUGIN.md: Updated version requirements

Root cause: Previous version bumps (0.9.0 → 0.9.1 → 0.9.2) only updated
cmd/bd/version.go, leaving other components out of sync.

The MCP server was initially versioned at 1.0.0 when added today, but
syncing to 0.9.2 for consistency since the project is still in alpha.

Closes bd-66

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

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

PLUGIN.md

@@ -277,6 +277,7 @@ This will show:
 ### Version Numbering
 
 Beads follows semantic versioning. The plugin version tracks the bd CLI version:
+- Plugin 0.9.2 requires bd CLI 0.9.2+
 - Plugin 0.9.x requires bd CLI 0.9.0+
 - Major version bumps may introduce breaking changes
 - Check CHANGELOG.md for release notes