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/src/bun/index.ts

@@ -0,0 +1,127 @@
+import z from "zod"
+import { Global } from "../global"
+import { Log } from "../util/log"
+import path from "path"
+import { Filesystem } from "../util/filesystem"
+import { NamedError } from "@opencode-ai/util/error"
+import { Lock } from "../util/lock"
+import { PackageRegistry } from "./registry"
+import { proxied } from "@/util/proxied"
+import { Process } from "../util/process"
+
+export namespace BunProc {
+  const log = Log.create({ service: "bun" })
+
+  export async function run(cmd: string[], options?: Process.RunOptions) {
+    const full = [which(), ...cmd]
+    log.info("running", {
+      cmd: full,
+      ...options,
+    })
+    const result = await Process.run(full, {
+      cwd: options?.cwd,
+      abort: options?.abort,
+      kill: options?.kill,
+      timeout: options?.timeout,
+      nothrow: options?.nothrow,
+      env: {
+        ...process.env,
+        ...options?.env,
+        BUN_BE_BUN: "1",
+      },
+    })
+    log.info("done", {
+      code: result.code,
+      stdout: result.stdout.toString(),
+      stderr: result.stderr.toString(),
+    })
+    return result
+  }
+
+  export function which() {
+    return process.execPath
+  }
+
+  export const InstallFailedError = NamedError.create(
+    "BunInstallFailedError",
+    z.object({
+      pkg: z.string(),
+      version: z.string(),
+    }),
+  )
+
+  export async function install(pkg: string, version = "latest") {
+    // Use lock to ensure only one install at a time
+    using _ = await Lock.write("bun-install")
+
+    const mod = path.join(Global.Path.cache, "node_modules", pkg)
+    const pkgjsonPath = path.join(Global.Path.cache, "package.json")
+    const parsed = await Filesystem.readJson<{ dependencies: Record<string, string> }>(pkgjsonPath).catch(async () => {
+      const result = { dependencies: {} as Record<string, string> }
+      await Filesystem.writeJson(pkgjsonPath, result)
+      return result
+    })
+    if (!parsed.dependencies) parsed.dependencies = {} as Record<string, string>
+    const dependencies = parsed.dependencies
+    const modExists = await Filesystem.exists(mod)
+    const cachedVersion = dependencies[pkg]
+
+    if (!modExists || !cachedVersion) {
+      // continue to install
+    } else if (version !== "latest" && cachedVersion === version) {
+      return mod
+    } else if (version === "latest") {
+      const isOutdated = await PackageRegistry.isOutdated(pkg, cachedVersion, Global.Path.cache)
+      if (!isOutdated) return mod
+      log.info("Cached version is outdated, proceeding with install", { pkg, cachedVersion })
+    }
+
+    // Build command arguments
+    const args = [
+      "add",
+      "--force",
+      "--exact",
+      // TODO: get rid of this case (see: https://github.com/oven-sh/bun/issues/19936)
+      ...(proxied() || process.env.CI ? ["--no-cache"] : []),
+      "--cwd",
+      Global.Path.cache,
+      pkg + "@" + version,
+    ]
+
+    // Let Bun handle registry resolution:
+    // - If .npmrc files exist, Bun will use them automatically
+    // - If no .npmrc files exist, Bun will default to https://registry.npmjs.org
+    // - No need to pass --registry flag
+    log.info("installing package using Bun's default registry resolution", {
+      pkg,
+      version,
+    })
+
+    await BunProc.run(args, {
+      cwd: Global.Path.cache,
+    }).catch((e) => {
+      throw new InstallFailedError(
+        { pkg, version },
+        {
+          cause: e,
+        },
+      )
+    })
+
+    // Resolve actual version from installed package when using "latest"
+    // This ensures subsequent starts use the cached version until explicitly updated
+    let resolvedVersion = version
+    if (version === "latest") {
+      const installedPkg = await Filesystem.readJson<{ version?: string }>(path.join(mod, "package.json")).catch(
+        () => null,
+      )
+      if (installedPkg?.version) {
+        resolvedVersion = installedPkg.version
+      }
+    }
+
+    parsed.dependencies[pkg] = resolvedVersion
+    await Filesystem.writeJson(pkgjsonPath, parsed)
+    return mod
+  }
+}

packages/tfcode/src/bun/registry.ts

@@ -0,0 +1,44 @@
+import semver from "semver"
+import { Log } from "../util/log"
+import { Process } from "../util/process"
+
+export namespace PackageRegistry {
+  const log = Log.create({ service: "bun" })
+
+  function which() {
+    return process.execPath
+  }
+
+  export async function info(pkg: string, field: string, cwd?: string): Promise<string | null> {
+    const { code, stdout, stderr } = await Process.run([which(), "info", pkg, field], {
+      cwd,
+      env: {
+        ...process.env,
+        BUN_BE_BUN: "1",
+      },
+      nothrow: true,
+    })
+
+    if (code !== 0) {
+      log.warn("bun info failed", { pkg, field, code, stderr: stderr.toString() })
+      return null
+    }
+
+    const value = stdout.toString().trim()
+    if (!value) return null
+    return value
+  }
+
+  export async function isOutdated(pkg: string, cachedVersion: string, cwd?: string): Promise<boolean> {
+    const latestVersion = await info(pkg, "version", cwd)
+    if (!latestVersion) {
+      log.warn("Failed to resolve latest version, using cached", { pkg, cachedVersion })
+      return false
+    }
+
+    const isRange = /[\s^~*xX<>|=]/.test(cachedVersion)
+    if (isRange) return !semver.satisfies(latestVersion, cachedVersion)
+
+    return semver.lt(cachedVersion, latestVersion)
+  }
+}