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/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)
+  }
+}