feat: ship verified platform upgrades with channel bundle releases

Package production dependencies per architecture for online and offline upgrades.
Validate dependencies and isolated backend startup before readiness, repair once
when permitted, and preserve service/data through failed preparation or rollback.

Publish release bundles with master images and expose an opt-in develop build
sharing the development index across Alpine and Debian images.

cli/test/internal/local.test.cjs

@@ -322,6 +322,10 @@ test(
   async (t) => {
     if (process.platform === 'win32') return t.skip('POSIX process groups');
     const { runProcess } = require('../../dist/internal/runtime/process');
+    const marker = path.join(sandbox(t), 'timeout');
+    const controller = new AbortController();
+    const guard = setTimeout(() => controller.abort(), 4000);
+    t.after(() => clearTimeout(guard));
     let descendant;
     t.after(() => {
       if (descendant)
@@ -329,13 +333,17 @@ test(
           process.kill(descendant, 'SIGKILL');
         } catch {}
     });
+    // Start the deadline only after the descendant installed its handlers.
+    // Cold Node startup under parallel load need not fit in 350 milliseconds.
     const grandchild =
-      'process.on("SIGINT",()=>{});process.on("SIGTERM",()=>{});console.log(process.pid);setInterval(()=>{},1000)';
+      'process.on("SIGINT",()=>{});process.on("SIGTERM",()=>{});console.log(process.pid);require("node:fs").writeSync(3,"T");setInterval(()=>{},1000)';
     const parent = `require('node:child_process').spawn(process.execPath,['-e',${JSON.stringify(
       grandchild,
-    )}],{stdio:['ignore',1,2]});setTimeout(()=>process.exit(0),100);`;
+    )}],{stdio:['ignore',1,2,3]});setTimeout(()=>process.exit(0),100);`;
     const result = await runProcess(process.execPath, ['-e', parent], {
       timeoutMs: 350,
+      timeoutControl: { marker },
+      signal: controller.signal,
       graceMs: 100,
       output: (chunk) => {
         const pid = Number(chunk.toString().trim());
@@ -345,6 +353,7 @@ test(
     assert.equal(result.code, 124);
     assert.equal(result.timedOut, true);
     assert.ok(descendant);
+    assert.equal(fs.existsSync(marker), true);
   },
 );