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/util/process.test.ts

@@ -0,0 +1,128 @@
+import { describe, expect, test } from "bun:test"
+import fs from "fs/promises"
+import path from "path"
+import { Process } from "../../src/util/process"
+import { tmpdir } from "../fixture/fixture"
+
+function node(script: string) {
+  return [process.execPath, "-e", script]
+}
+
+describe("util.process", () => {
+  test("captures stdout and stderr", async () => {
+    const out = await Process.run(node('process.stdout.write("out");process.stderr.write("err")'))
+    expect(out.code).toBe(0)
+    expect(out.stdout.toString()).toBe("out")
+    expect(out.stderr.toString()).toBe("err")
+  })
+
+  test("returns code when nothrow is enabled", async () => {
+    const out = await Process.run(node("process.exit(7)"), { nothrow: true })
+    expect(out.code).toBe(7)
+  })
+
+  test("throws RunFailedError on non-zero exit", async () => {
+    const err = await Process.run(node('process.stderr.write("bad");process.exit(3)')).catch((error) => error)
+    expect(err).toBeInstanceOf(Process.RunFailedError)
+    if (!(err instanceof Process.RunFailedError)) throw err
+    expect(err.code).toBe(3)
+    expect(err.stderr.toString()).toBe("bad")
+  })
+
+  test("aborts a running process", async () => {
+    const abort = new AbortController()
+    const started = Date.now()
+    setTimeout(() => abort.abort(), 25)
+
+    const out = await Process.run(node("setInterval(() => {}, 1000)"), {
+      abort: abort.signal,
+      nothrow: true,
+    })
+
+    expect(out.code).not.toBe(0)
+    expect(Date.now() - started).toBeLessThan(1000)
+  }, 3000)
+
+  test("kills after timeout when process ignores terminate signal", async () => {
+    if (process.platform === "win32") return
+
+    const abort = new AbortController()
+    const started = Date.now()
+    setTimeout(() => abort.abort(), 25)
+
+    const out = await Process.run(node('process.on("SIGTERM", () => {}); setInterval(() => {}, 1000)'), {
+      abort: abort.signal,
+      nothrow: true,
+      timeout: 25,
+    })
+
+    expect(out.code).not.toBe(0)
+    expect(Date.now() - started).toBeLessThan(1000)
+  }, 3000)
+
+  test("uses cwd when spawning commands", async () => {
+    await using tmp = await tmpdir()
+    const out = await Process.run(node("process.stdout.write(process.cwd())"), {
+      cwd: tmp.path,
+    })
+    expect(out.stdout.toString()).toBe(tmp.path)
+  })
+
+  test("merges environment overrides", async () => {
+    const out = await Process.run(node('process.stdout.write(process.env.OPENCODE_TEST ?? "")'), {
+      env: {
+        OPENCODE_TEST: "set",
+      },
+    })
+    expect(out.stdout.toString()).toBe("set")
+  })
+
+  test("uses shell in run on Windows", async () => {
+    if (process.platform !== "win32") return
+
+    const out = await Process.run(["set", "OPENCODE_TEST_SHELL"], {
+      shell: true,
+      env: {
+        OPENCODE_TEST_SHELL: "ok",
+      },
+    })
+
+    expect(out.code).toBe(0)
+    expect(out.stdout.toString()).toContain("OPENCODE_TEST_SHELL=ok")
+  })
+
+  test("runs cmd scripts with spaces on Windows without shell", async () => {
+    if (process.platform !== "win32") return
+
+    await using tmp = await tmpdir()
+    const dir = path.join(tmp.path, "with space")
+    const file = path.join(dir, "echo cmd.cmd")
+
+    await fs.mkdir(dir, { recursive: true })
+    await Bun.write(file, "@echo off\r\nif %~1==--stdio exit /b 0\r\nexit /b 7\r\n")
+
+    const proc = Process.spawn([file, "--stdio"], {
+      stdin: "pipe",
+      stdout: "pipe",
+      stderr: "pipe",
+    })
+
+    expect(await proc.exited).toBe(0)
+  })
+
+  test("rejects missing commands without leaking unhandled errors", async () => {
+    await using tmp = await tmpdir()
+    const cmd = path.join(tmp.path, "missing" + (process.platform === "win32" ? ".cmd" : ""))
+    const err = await Process.spawn([cmd], {
+      stdin: "pipe",
+      stdout: "pipe",
+      stderr: "pipe",
+    }).exited.catch((err) => err)
+
+    expect(err).toBeInstanceOf(Error)
+    if (!(err instanceof Error)) throw err
+    expect(err).toMatchObject({
+      code: "ENOENT",
+    })
+  })
+})