Build on bun 1.3.13 to fix the Windows TUI (OpenTUI FFI crash)

`utmstack` crashed at startup on Windows with:
  Failed to initialize OpenTUI render library: bun:ffi dlopen() is not
  available in this build (TinyCC is disabled)

Root cause is Bun issue #30717: a regression that landed in bun 1.3.14 (the
Rust rewrite) drops the extraction step for FFI native libraries embedded via
`with: {type:"file"}` in `bun build --compile` output. OpenTUI — opencode's
renderer — loads its native library exactly that way, so the compiled binary
cannot dlopen it. On macOS/Linux a fallback masks it; on Windows, where TinyCC
is also disabled in compiled binaries, both paths fail and the TUI won't start.
1.3.14 is the latest Bun release and the fix (PR #30720) is in no release, so
the only path is to build on 1.3.13, the last release before the regression.

Verified on a real Windows 11 ARM64 machine: the 1.3.14 build exits immediately
with the FFI error; the 1.3.13 build gets past renderer init and runs. macOS
arm64 rebuilt on 1.3.13 and TUI-smoke-tested — no regression.

Pins packageManager and CI setup-bun to 1.3.13. Adds a BUILD_TARGETS env filter
to build.ts so a single platform can be built for testing without the full
matrix.

I had not tested the interactive TUI on Windows before the first release — only
the MCP end-to-end and the CLI's headless `run` path on macOS. That gap is what
let this ship. The release workflow's verify step still only checks --version;
a TUI smoke test in CI is a follow-up worth doing.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: Rick Valdes

.github/workflows/utmstack-release.yml

@@ -46,7 +46,7 @@ jobs:
 
       - uses: oven-sh/setup-bun@v2
         with:
-          bun-version: 1.3.14
+          bun-version: 1.3.13
 
       - name: Resolve version
         id: version

package.json

@@ -4,7 +4,7 @@
   "description": "AI-powered development tool",
   "private": true,
   "type": "module",
-  "packageManager": "bun@1.3.14",
+  "packageManager": "bun@1.3.13",
   "scripts": {
     "dev": "bun run --cwd packages/opencode --conditions=browser src/index.ts",
     "dev:desktop": "bun --cwd packages/desktop dev",

packages/opencode/script/build.ts

@@ -116,7 +116,15 @@ const allTargets: {
   },
 ]
 
-const targets = singleFlag
+// BUILD_TARGETS=win32-arm64,linux-x64 restricts the build to specific targets
+// (matched as "<os>-<arch>[-baseline][-<abi>]"). Used for testing one platform
+// without a full matrix build.
+const onlyTargets = process.env.BUILD_TARGETS?.split(",").map((x) => x.trim()).filter(Boolean)
+const targetKey = (t) =>
+  `${t.os}-${t.arch}${t.avx2 === false ? "-baseline" : ""}${t.abi ? "-" + t.abi : ""}`
+const targets = onlyTargets
+  ? allTargets.filter((item) => onlyTargets.includes(targetKey(item)))
+  : singleFlag
   ? allTargets.filter((item) => {
       if (item.os !== process.platform || item.arch !== process.arch) {
         return false