move pi-mono into companion-cloud as apps/companion-os

- Copy all pi-mono source into apps/companion-os/
- Update Dockerfile to COPY pre-built binary instead of downloading from GitHub Releases
- Update deploy-staging.yml to build pi from source (bun compile) before Docker build
- Add apps/companion-os/** to path triggers
- No more cross-repo dispatch needed

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/ai/test/transform-messages-copilot-openai-to-anthropic.test.ts

@@ -0,0 +1,140 @@
+import { describe, expect, it } from "vitest";
+import { transformMessages } from "../src/providers/transform-messages.js";
+import type {
+  AssistantMessage,
+  Message,
+  Model,
+  ToolCall,
+} from "../src/types.js";
+
+// Normalize function matching what anthropic.ts uses
+function anthropicNormalizeToolCallId(
+  id: string,
+  _model: Model<"anthropic-messages">,
+  _source: AssistantMessage,
+): string {
+  return id.replace(/[^a-zA-Z0-9_-]/g, "_").slice(0, 64);
+}
+
+function makeCopilotClaudeModel(): Model<"anthropic-messages"> {
+  return {
+    id: "claude-sonnet-4",
+    name: "Claude Sonnet 4",
+    api: "anthropic-messages",
+    provider: "github-copilot",
+    baseUrl: "https://api.individual.githubcopilot.com",
+    reasoning: true,
+    input: ["text", "image"],
+    cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+    contextWindow: 128000,
+    maxTokens: 16000,
+  };
+}
+
+describe("OpenAI to Anthropic session migration for Copilot Claude", () => {
+  it("converts thinking blocks to plain text when source model differs", () => {
+    const model = makeCopilotClaudeModel();
+    const messages: Message[] = [
+      { role: "user", content: "hello", timestamp: Date.now() },
+      {
+        role: "assistant",
+        content: [
+          {
+            type: "thinking",
+            thinking: "Let me think about this...",
+            thinkingSignature: "reasoning_content",
+          },
+          { type: "text", text: "Hi there!" },
+        ],
+        api: "openai-completions",
+        provider: "github-copilot",
+        model: "gpt-4o",
+        usage: {
+          input: 0,
+          output: 0,
+          cacheRead: 0,
+          cacheWrite: 0,
+          totalTokens: 0,
+          cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
+        },
+        stopReason: "stop",
+        timestamp: Date.now(),
+      },
+    ];
+
+    const result = transformMessages(
+      messages,
+      model,
+      anthropicNormalizeToolCallId,
+    );
+    const assistantMsg = result.find(
+      (m) => m.role === "assistant",
+    ) as AssistantMessage;
+
+    // Thinking block should be converted to text since models differ
+    const textBlocks = assistantMsg.content.filter((b) => b.type === "text");
+    const thinkingBlocks = assistantMsg.content.filter(
+      (b) => b.type === "thinking",
+    );
+    expect(thinkingBlocks).toHaveLength(0);
+    expect(textBlocks.length).toBeGreaterThanOrEqual(2);
+  });
+
+  it("removes thoughtSignature from tool calls when migrating between models", () => {
+    const model = makeCopilotClaudeModel();
+    const messages: Message[] = [
+      { role: "user", content: "run a command", timestamp: Date.now() },
+      {
+        role: "assistant",
+        content: [
+          {
+            type: "toolCall",
+            id: "call_123",
+            name: "bash",
+            arguments: { command: "ls" },
+            thoughtSignature: JSON.stringify({
+              type: "reasoning.encrypted",
+              id: "call_123",
+              data: "encrypted",
+            }),
+          },
+        ],
+        api: "openai-responses",
+        provider: "github-copilot",
+        model: "gpt-5",
+        usage: {
+          input: 0,
+          output: 0,
+          cacheRead: 0,
+          cacheWrite: 0,
+          totalTokens: 0,
+          cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
+        },
+        stopReason: "toolUse",
+        timestamp: Date.now(),
+      },
+      {
+        role: "toolResult",
+        toolCallId: "call_123",
+        toolName: "bash",
+        content: [{ type: "text", text: "output" }],
+        isError: false,
+        timestamp: Date.now(),
+      },
+    ];
+
+    const result = transformMessages(
+      messages,
+      model,
+      anthropicNormalizeToolCallId,
+    );
+    const assistantMsg = result.find(
+      (m) => m.role === "assistant",
+    ) as AssistantMessage;
+    const toolCall = assistantMsg.content.find(
+      (b) => b.type === "toolCall",
+    ) as ToolCall;
+
+    expect(toolCall.thoughtSignature).toBeUndefined();
+  });
+});