refactor: finish companion rename migration

Complete the remaining pi-to-companion rename across companion-os, web, vm-orchestrator, docker, and archived fixtures.

Verification:
- semantic rg sweeps for Pi/piConfig/getPi/.pi runtime references
- npm run check in apps/companion-os (fails in this worktree: biome not found)

Co-authored-by: Codex <noreply@openai.com>

packages/agent/package.json

@@ -1,5 +1,5 @@
 {
-  "name": "@mariozechner/pi-agent-core",
+  "name": "@mariozechner/companion-agent-core",
   "version": "0.56.2",
   "description": "General-purpose agent with transport abstraction, state management, and attachment support",
   "type": "module",
@@ -17,7 +17,7 @@
     "prepublishOnly": "npm run clean && npm run build"
   },
   "dependencies": {
-    "@mariozechner/pi-ai": "^0.56.2"
+    "@mariozechner/companion-ai": "^0.56.2"
   },
   "keywords": [
     "ai",