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/lazy.test.ts

@@ -0,0 +1,50 @@
+import { describe, expect, test } from "bun:test"
+import { lazy } from "../../src/util/lazy"
+
+describe("util.lazy", () => {
+  test("should call function only once", () => {
+    let callCount = 0
+    const getValue = () => {
+      callCount++
+      return "expensive value"
+    }
+
+    const lazyValue = lazy(getValue)
+
+    expect(callCount).toBe(0)
+
+    const result1 = lazyValue()
+    expect(result1).toBe("expensive value")
+    expect(callCount).toBe(1)
+
+    const result2 = lazyValue()
+    expect(result2).toBe("expensive value")
+    expect(callCount).toBe(1)
+  })
+
+  test("should preserve the same reference", () => {
+    const obj = { value: 42 }
+    const lazyObj = lazy(() => obj)
+
+    const result1 = lazyObj()
+    const result2 = lazyObj()
+
+    expect(result1).toBe(obj)
+    expect(result2).toBe(obj)
+    expect(result1).toBe(result2)
+  })
+
+  test("should work with different return types", () => {
+    const lazyString = lazy(() => "string")
+    const lazyNumber = lazy(() => 123)
+    const lazyBoolean = lazy(() => true)
+    const lazyNull = lazy(() => null)
+    const lazyUndefined = lazy(() => undefined)
+
+    expect(lazyString()).toBe("string")
+    expect(lazyNumber()).toBe(123)
+    expect(lazyBoolean()).toBe(true)
+    expect(lazyNull()).toBe(null)
+    expect(lazyUndefined()).toBe(undefined)
+  })
+})