fix(compound-engineering): break dashboard dependency cycle

A new workspace-acyclicity invariant on main (run via the PR merge) flagged
compound-engineering -> @fusion/dashboard -> compound-engineering: the plugin is
listed in @fusion/dashboard's deps (for view loading) AND declared @fusion/dashboard
as a runtime dependency, which the cycle check (deps+devDeps) and the
'bundled plugins must not depend on host packages' check both reject.

The plugin's only @fusion/dashboard use is the type-only PluginDashboardViewContext
import. Drop the @fusion/dashboard dependency and resolve that type via an ambient
dashboard-interop.d.ts + tsconfig paths mapping (the fusion-plugin-dependency-graph
interop pattern). Breaks the cycle; the host passes the real context at runtime.

plugins/fusion-plugin-compound-engineering/package.json

@@ -20,7 +20,6 @@
   },
   "dependencies": {
     "@fusion/core": "workspace:*",
-    "@fusion/dashboard": "workspace:*",
     "@fusion/plugin-sdk": "workspace:*",
     "lucide-react": "^0.542.0",
     "react": "^19.0.0",