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/session/todo.ts

@@ -0,0 +1,57 @@
+import { BusEvent } from "@/bus/bus-event"
+import { Bus } from "@/bus"
+import { SessionID } from "./schema"
+import z from "zod"
+import { Database, eq, asc } from "../storage/db"
+import { TodoTable } from "./session.sql"
+
+export namespace Todo {
+  export const Info = z
+    .object({
+      content: z.string().describe("Brief description of the task"),
+      status: z.string().describe("Current status of the task: pending, in_progress, completed, cancelled"),
+      priority: z.string().describe("Priority level of the task: high, medium, low"),
+    })
+    .meta({ ref: "Todo" })
+  export type Info = z.infer<typeof Info>
+
+  export const Event = {
+    Updated: BusEvent.define(
+      "todo.updated",
+      z.object({
+        sessionID: SessionID.zod,
+        todos: z.array(Info),
+      }),
+    ),
+  }
+
+  export function update(input: { sessionID: SessionID; todos: Info[] }) {
+    Database.transaction((db) => {
+      db.delete(TodoTable).where(eq(TodoTable.session_id, input.sessionID)).run()
+      if (input.todos.length === 0) return
+      db.insert(TodoTable)
+        .values(
+          input.todos.map((todo, position) => ({
+            session_id: input.sessionID,
+            content: todo.content,
+            status: todo.status,
+            priority: todo.priority,
+            position,
+          })),
+        )
+        .run()
+    })
+    Bus.publish(Event.Updated, input)
+  }
+
+  export function get(sessionID: SessionID) {
+    const rows = Database.use((db) =>
+      db.select().from(TodoTable).where(eq(TodoTable.session_id, sessionID)).orderBy(asc(TodoTable.position)).all(),
+    )
+    return rows.map((row) => ({
+      content: row.content,
+      status: row.status,
+      priority: row.priority,
+    }))
+  }
+}