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/src/util/lazy.ts

@@ -0,0 +1,23 @@
+export function lazy<T>(fn: () => T) {
+  let value: T | undefined
+  let loaded = false
+
+  const result = (): T => {
+    if (loaded) return value as T
+    try {
+      value = fn()
+      loaded = true
+      return value as T
+    } catch (e) {
+      // Don't mark as loaded if initialization failed
+      throw e
+    }
+  }
+
+  result.reset = () => {
+    loaded = false
+    value = undefined
+  }
+
+  return result
+}