build: 精简构建目标为 5 个主平台

allTargets 只保留 win-x64/darwin-arm64/darwin-x64/linux-x64/linux-arm64，
去掉 musl/baseline 变体，加快构建、减少体积。
去掉 --single 即一次构建全部 5 平台（Bun 交叉编译）。

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

packages/opencode/script/build.ts

@@ -56,34 +56,13 @@ const allTargets: {
   abi?: "musl"
   avx2?: false
 }[] = [
-  {
-    os: "linux",
-    arch: "arm64",
-  },
   {
     os: "linux",
     arch: "x64",
   },
-  {
-    os: "linux",
-    arch: "x64",
-    avx2: false,
-  },
   {
     os: "linux",
     arch: "arm64",
-    abi: "musl",
-  },
-  {
-    os: "linux",
-    arch: "x64",
-    abi: "musl",
-  },
-  {
-    os: "linux",
-    arch: "x64",
-    abi: "musl",
-    avx2: false,
   },
   {
     os: "darwin",
@@ -93,24 +72,10 @@ const allTargets: {
     os: "darwin",
     arch: "x64",
   },
-  {
-    os: "darwin",
-    arch: "x64",
-    avx2: false,
-  },
-  {
-    os: "win32",
-    arch: "arm64",
-  },
   {
     os: "win32",
     arch: "x64",
   },
-  {
-    os: "win32",
-    arch: "x64",
-    avx2: false,
-  },
 ]
 
 const targets = singleFlag