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/tsconfig.json

@@ -0,0 +1,23 @@
+{
+  "$schema": "https://json.schemastore.org/tsconfig",
+  "extends": "@tsconfig/bun/tsconfig.json",
+  "compilerOptions": {
+    "jsx": "preserve",
+    "jsxImportSource": "@opentui/solid",
+    "lib": ["ESNext", "DOM", "DOM.Iterable"],
+    "types": [],
+    "noUncheckedIndexedAccess": false,
+    "customConditions": ["browser"],
+    "paths": {
+      "@/*": ["./src/*"],
+      "@tui/*": ["./src/cli/cmd/tui/*"]
+    },
+    "plugins": [
+      {
+        "name": "@effect/language-service",
+        "transform": "@effect/language-service/transform",
+        "namespaceImportPackages": ["effect", "@effect/*"]
+      }
+    ]
+  }
+}