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/installation/installation.test.ts

@@ -0,0 +1,151 @@
+import { describe, expect, test } from "bun:test"
+import { Effect, Layer, Stream } from "effect"
+import { HttpClient, HttpClientRequest, HttpClientResponse } from "effect/unstable/http"
+import { ChildProcess, ChildProcessSpawner } from "effect/unstable/process"
+import { Installation } from "../../src/installation"
+
+const encoder = new TextEncoder()
+
+function mockHttpClient(handler: (request: HttpClientRequest.HttpClientRequest) => Response) {
+  const client = HttpClient.make((request) => Effect.succeed(HttpClientResponse.fromWeb(request, handler(request))))
+  return Layer.succeed(HttpClient.HttpClient, client)
+}
+
+function mockSpawner(handler: (cmd: string, args: readonly string[]) => string = () => "") {
+  const spawner = ChildProcessSpawner.make((command) => {
+    const std = ChildProcess.isStandardCommand(command) ? command : undefined
+    const output = handler(std?.command ?? "", std?.args ?? [])
+    return Effect.succeed(
+      ChildProcessSpawner.makeHandle({
+        pid: ChildProcessSpawner.ProcessId(0),
+        exitCode: Effect.succeed(ChildProcessSpawner.ExitCode(0)),
+        isRunning: Effect.succeed(false),
+        kill: () => Effect.void,
+        stdin: { [Symbol.for("effect/Sink/TypeId")]: Symbol.for("effect/Sink/TypeId") } as any,
+        stdout: output ? Stream.make(encoder.encode(output)) : Stream.empty,
+        stderr: Stream.empty,
+        all: Stream.empty,
+        getInputFd: () => ({ [Symbol.for("effect/Sink/TypeId")]: Symbol.for("effect/Sink/TypeId") }) as any,
+        getOutputFd: () => Stream.empty,
+      }),
+    )
+  })
+  return Layer.succeed(ChildProcessSpawner.ChildProcessSpawner, spawner)
+}
+
+function jsonResponse(body: unknown) {
+  return new Response(JSON.stringify(body), {
+    status: 200,
+    headers: { "content-type": "application/json" },
+  })
+}
+
+function testLayer(
+  httpHandler: (request: HttpClientRequest.HttpClientRequest) => Response,
+  spawnHandler?: (cmd: string, args: readonly string[]) => string,
+) {
+  return Installation.layer.pipe(Layer.provide(mockHttpClient(httpHandler)), Layer.provide(mockSpawner(spawnHandler)))
+}
+
+describe("installation", () => {
+  describe("latest", () => {
+    test("reads release version from GitHub releases", async () => {
+      const layer = testLayer(() => jsonResponse({ tag_name: "v1.2.3" }))
+
+      const result = await Effect.runPromise(
+        Installation.Service.use((svc) => svc.latest("unknown")).pipe(Effect.provide(layer)),
+      )
+      expect(result).toBe("1.2.3")
+    })
+
+    test("strips v prefix from GitHub release tag", async () => {
+      const layer = testLayer(() => jsonResponse({ tag_name: "v4.0.0-beta.1" }))
+
+      const result = await Effect.runPromise(
+        Installation.Service.use((svc) => svc.latest("curl")).pipe(Effect.provide(layer)),
+      )
+      expect(result).toBe("4.0.0-beta.1")
+    })
+
+    test("reads npm registry versions", async () => {
+      const layer = testLayer(
+        () => jsonResponse({ version: "1.5.0" }),
+        (cmd, args) => {
+          if (cmd === "npm" && args.includes("registry")) return "https://registry.npmjs.org\n"
+          return ""
+        },
+      )
+
+      const result = await Effect.runPromise(
+        Installation.Service.use((svc) => svc.latest("npm")).pipe(Effect.provide(layer)),
+      )
+      expect(result).toBe("1.5.0")
+    })
+
+    test("reads npm registry versions for bun method", async () => {
+      const layer = testLayer(
+        () => jsonResponse({ version: "1.6.0" }),
+        () => "",
+      )
+
+      const result = await Effect.runPromise(
+        Installation.Service.use((svc) => svc.latest("bun")).pipe(Effect.provide(layer)),
+      )
+      expect(result).toBe("1.6.0")
+    })
+
+    test("reads scoop manifest versions", async () => {
+      const layer = testLayer(() => jsonResponse({ version: "2.3.4" }))
+
+      const result = await Effect.runPromise(
+        Installation.Service.use((svc) => svc.latest("scoop")).pipe(Effect.provide(layer)),
+      )
+      expect(result).toBe("2.3.4")
+    })
+
+    test("reads chocolatey feed versions", async () => {
+      const layer = testLayer(() => jsonResponse({ d: { results: [{ Version: "3.4.5" }] } }))
+
+      const result = await Effect.runPromise(
+        Installation.Service.use((svc) => svc.latest("choco")).pipe(Effect.provide(layer)),
+      )
+      expect(result).toBe("3.4.5")
+    })
+
+    test("reads brew formulae API versions", async () => {
+      const layer = testLayer(
+        () => jsonResponse({ versions: { stable: "2.0.0" } }),
+        (cmd, args) => {
+          // getBrewFormula: return core formula (no tap)
+          if (cmd === "brew" && args.includes("--formula") && args.includes("anomalyco/tap/opencode")) return ""
+          if (cmd === "brew" && args.includes("--formula") && args.includes("opencode")) return "opencode"
+          return ""
+        },
+      )
+
+      const result = await Effect.runPromise(
+        Installation.Service.use((svc) => svc.latest("brew")).pipe(Effect.provide(layer)),
+      )
+      expect(result).toBe("2.0.0")
+    })
+
+    test("reads brew tap info JSON via CLI", async () => {
+      const brewInfoJson = JSON.stringify({
+        formulae: [{ versions: { stable: "2.1.0" } }],
+      })
+      const layer = testLayer(
+        () => jsonResponse({}), // HTTP not used for tap formula
+        (cmd, args) => {
+          if (cmd === "brew" && args.includes("anomalyco/tap/opencode") && args.includes("--formula")) return "opencode"
+          if (cmd === "brew" && args.includes("--json=v2")) return brewInfoJson
+          return ""
+        },
+      )
+
+      const result = await Effect.runPromise(
+        Installation.Service.use((svc) => svc.latest("brew")).pipe(Effect.provide(layer)),
+      )
+      expect(result).toBe("2.1.0")
+    })
+  })
+})