refactor: apply minimal tfcode branding

- Rename packages/opencode → packages/tfcode (directory only)
- Rename bin/opencode → bin/tfcode (CLI binary)
- Rename .opencode → .tfcode (config directory)
- Update package.json name and bin field
- Update config directory path references (.tfcode)
- Keep internal code references as 'opencode' for easy upstream sync
- Keep @opencode-ai/* workspace package names

This minimal branding approach allows clean merges from upstream
opencode repository while providing tfcode branding for users.

packages/tfcode/test/util/timeout.test.ts

@@ -0,0 +1,21 @@
+import { describe, expect, test } from "bun:test"
+import { withTimeout } from "../../src/util/timeout"
+
+describe("util.timeout", () => {
+  test("should resolve when promise completes before timeout", async () => {
+    const fastPromise = new Promise<string>((resolve) => {
+      setTimeout(() => resolve("fast"), 10)
+    })
+
+    const result = await withTimeout(fastPromise, 100)
+    expect(result).toBe("fast")
+  })
+
+  test("should reject when promise exceeds timeout", async () => {
+    const slowPromise = new Promise<string>((resolve) => {
+      setTimeout(() => resolve("slow"), 200)
+    })
+
+    await expect(withTimeout(slowPromise, 50)).rejects.toThrow("Operation timed out after 50ms")
+  })
+})