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/iife.test.ts

@@ -0,0 +1,36 @@
+import { describe, expect, test } from "bun:test"
+import { iife } from "../../src/util/iife"
+
+describe("util.iife", () => {
+  test("should execute function immediately and return result", () => {
+    let called = false
+    const result = iife(() => {
+      called = true
+      return 42
+    })
+
+    expect(called).toBe(true)
+    expect(result).toBe(42)
+  })
+
+  test("should work with async functions", async () => {
+    let called = false
+    const result = await iife(async () => {
+      called = true
+      return "async result"
+    })
+
+    expect(called).toBe(true)
+    expect(result).toBe("async result")
+  })
+
+  test("should handle functions with no return value", () => {
+    let called = false
+    const result = iife(() => {
+      called = true
+    })
+
+    expect(called).toBe(true)
+    expect(result).toBeUndefined()
+  })
+})