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/file/ignore.test.ts

@@ -0,0 +1,10 @@
+import { test, expect } from "bun:test"
+import { FileIgnore } from "../../src/file/ignore"
+
+test("match nested and non-nested", () => {
+  expect(FileIgnore.match("node_modules/index.js")).toBe(true)
+  expect(FileIgnore.match("node_modules")).toBe(true)
+  expect(FileIgnore.match("node_modules/")).toBe(true)
+  expect(FileIgnore.match("node_modules/bar")).toBe(true)
+  expect(FileIgnore.match("node_modules/bar/")).toBe(true)
+})