chore: US-028 bridge fixes for Pi interactive TUI

- Fix process.kill(self, SIGWINCH) to dispatch signal handlers instead of
  exiting — Pi TUI sends SIGWINCH to refresh dimensions on startup
- Add _stdinRead to ASYNC_BRIDGE_FNS in V8 sidecar to prevent event loop
  deadlock when process.stdin.resume() starts the readLoop
- Rewrite pi-interactive.test.ts: remove all sandboxSkip/probe logic,
  use networkAdapter instead of inline fetch patching, ESM mode with
  PI_MAIN (avoids undici import issues with cli.js), proper env vars
- Tests still fail due to additional V8 sidecar crash during Pi TUI init
  (further sandbox gaps to investigate)

Author: NathanFlurry

native/v8-runtime/src/session.rs

@@ -678,7 +678,7 @@ pub(crate) const SYNC_BRIDGE_FNS: [&str; 31] = [
     "_childProcessSpawnSync",
 ];
 
-pub(crate) const ASYNC_BRIDGE_FNS: [&str; 7] = [
+pub(crate) const ASYNC_BRIDGE_FNS: [&str; 8] = [
     // Module loading (async)
     "_dynamicImport",
     // Timer
@@ -689,6 +689,8 @@ pub(crate) const ASYNC_BRIDGE_FNS: [&str; 7] = [
     "_networkHttpRequestRaw",
     "_networkHttpServerListenRaw",
     "_networkHttpServerCloseRaw",
+    // Streaming stdin (async — must not block V8 thread)
+    "_stdinRead",
 ];
 
 /// Run the session event loop: dispatch incoming messages to V8.

packages/nodejs/src/bridge/process.ts

@@ -870,9 +870,22 @@ const process: Record<string, unknown> & {
       err.syscall = "kill";
       throw err;
     }
-    // Resolve signal name to number (default SIGTERM)
+    // Resolve signal name to number and string
     const sigNum = _resolveSignal(signal);
-    // Self-kill - exit with 128 + signal number (POSIX convention)
+    const sigName = typeof signal === "string" ? signal
+      : Object.entries(_signalNumbers).find(([, n]) => n === sigNum)?.[0] ?? `SIG${sigNum}`;
+
+    // Signals with no default termination action (harmless if no handler)
+    const _harmlessSignals = new Set([28 /* SIGWINCH */, 17 /* SIGCHLD */, 23 /* SIGURG */, 18 /* SIGCONT */]);
+
+    // Try dispatching to registered signal handlers first
+    const handled = _emit(sigName, sigName);
+    if (handled) return true;
+
+    // No handler — harmless signals are silently ignored (POSIX behavior)
+    if (_harmlessSignals.has(sigNum)) return true;
+
+    // No handler for fatal signal — exit with 128 + signal number (POSIX convention)
     return (process as unknown as { exit: (code: number) => never }).exit(128 + sigNum);
   },