fix: kill orphaned process on Windows before OpenCode restart

killProcessOnPort() was a no-op on win32 (POSIX-only, via lsof/kill),
so a restart could leave the old OpenCode process holding the port
while a new instance spawned on a different one. That's a plausible
contributor to a chronic pattern seen in production logs: repeated
"OpenCode process exited, restarting" cycles and hundreds of
ECONNRESET/proxy errors over multiple days on Windows.

Give killProcessOnPort a real Windows branch: parse `netstat -ano`
for PIDs listening on the target port, filter out our own pid, and
force-kill each via `taskkill /PID <pid> /F` (no /T -- we don't own
that process, so only the listener itself is killed, not any
children it may have).

waitForPortRelease()'s existing soft-fail-and-warn behavior is left
untouched -- it's a deliberate safety net for any platform where the
port doesn't free up in time, not just Windows, and the restart
already rebinds event-stream readers to the actual resulting port via
onOpenCodeRestarted.

packages/web/server/lib/opencode/lifecycle.js

@@ -53,8 +53,35 @@ export const createOpenCodeLifecycleRuntime = (deps) => {
     now = Date.now,
   } = deps;
 
+  const killProcessOnPortWin32 = (port) => {
+    try {
+      const result = spawnSync('netstat', ['-ano'], { encoding: 'utf8', timeout: 5000, windowsHide: true });
+      const output = result.stdout || '';
+      const myPid = process.pid;
+      const listeningPidPattern = /^\s*TCP\s+\S*:(\d+)\s+\S+\s+LISTENING\s+(\d+)\s*$/gim;
+      const pids = new Set();
+      let match;
+      while ((match = listeningPidPattern.exec(output)) !== null) {
+        if (Number.parseInt(match[1], 10) !== port) continue;
+        const pid = Number.parseInt(match[2], 10);
+        if (pid && pid !== myPid) pids.add(pid);
+      }
+      for (const pid of pids) {
+        try {
+          spawnSync('taskkill', ['/PID', String(pid), '/F'], { stdio: 'ignore', timeout: 3000, windowsHide: true });
+        } catch {
+        }
+      }
+    } catch {
+    }
+  };
+
   const killProcessOnPort = (port) => {
-    if (!port || process.platform === 'win32') return;
+    if (!port) return;
+    if (process.platform === 'win32') {
+      killProcessOnPortWin32(port);
+      return;
+    }
     try {
       const result = spawnSync('lsof', ['-ti', `:${port}`], { encoding: 'utf8', timeout: 5000, windowsHide: true });
       const output = result.stdout || '';
@@ -698,10 +725,11 @@ export const createOpenCodeLifecycleRuntime = (deps) => {
       }
 
       // The restart may have landed on a NEW port (the old one can remain
-      // occupied by an orphaned process, e.g. Windows killProcessOnPort is a
-      // no-op). Upstream event readers pinned to the old process would keep
-      // the UI silent forever, so rebind them to the current port. Best
-      // effort: a failure here must not fail the restart itself.
+      // occupied if killProcessOnPort/waitForPortRelease didn't free it in
+      // time, on any platform). Upstream event readers pinned to the old
+      // process would keep the UI silent forever, so rebind them to the
+      // current port. Best effort: a failure here must not fail the restart
+      // itself.
       try {
         onOpenCodeRestarted?.();
       } catch (error) {