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/pi-grind/package.json

@@ -1,35 +0,0 @@
-{
-  "name": "pi-grind",
-  "version": "0.1.0",
-  "description": "Explicit grind mode for pi with durable follow-up continuation in daemon mode",
-  "type": "module",
-  "keywords": [
-    "pi-package"
-  ],
-  "license": "MIT",
-  "author": "Mario Zechner",
-  "main": "./src/index.ts",
-  "files": [
-    "src",
-    "test",
-    "package.json",
-    "README.md"
-  ],
-  "pi": {
-    "extensions": [
-      "./src/index.ts"
-    ]
-  },
-  "peerDependencies": {
-    "@mariozechner/pi-agent-core": "*",
-    "@mariozechner/pi-coding-agent": "*"
-  },
-  "devDependencies": {
-    "@types/node": "^24.3.0",
-    "typescript": "^5.9.3",
-    "vitest": "^3.2.4"
-  },
-  "scripts": {
-    "test": "vitest --run"
-  }
-}