feat(FN-2944): merge fusion/fn-2944

- test(FN-2944): cover already checked out worktree conflict recovery
- fix(FN-2944): recognize git already checked out worktree conflict
- fix(engine): auto-recover from squash-merge orphan rebase failures

Fusion-Task-Id: FN-2944

packages/pi-claude-cli/src/__tests__/setup-test-isolation.ts

@@ -4,3 +4,11 @@ import { join } from "node:path";
 
 const tempHome = mkdtempSync(join(tmpdir(), "fn-test-home-"));
 process.env.HOME = tempHome;
+process.env.USERPROFILE = tempHome;
+if (process.platform === "win32") {
+  const match = tempHome.match(/^([A-Za-z]:)(.*)$/);
+  if (match) {
+    process.env.HOMEDRIVE = match[1];
+    process.env.HOMEPATH = match[2] || "\\";
+  }
+}

packages/pi-claude-cli/src/prompt-builder.ts

@@ -615,7 +615,8 @@ function resolveAgentsMdPath(cwd: string): string | undefined {
   }
 
   // Fall back to global path
-  const globalPath = join(homedir(), ".pi", "agent", "AGENTS.md");
+  const globalHome = process.env.HOME || process.env.USERPROFILE || homedir();
+  const globalPath = join(globalHome, ".pi", "agent", "AGENTS.md");
   if (existsSync(globalPath)) return globalPath;
 
   return undefined;