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/drizzle.config.ts

@@ -0,0 +1,10 @@
+import { defineConfig } from "drizzle-kit"
+
+export default defineConfig({
+  dialect: "sqlite",
+  schema: "./src/**/*.sql.ts",
+  out: "./migration",
+  dbCredentials: {
+    url: "/home/thdxr/.local/share/opencode/opencode.db",
+  },
+})