feat(debugger): integrate NX Tcl Remote Debugger into NX Postprocessor

Embed the NX Tcl Remote Debugger into the NX Postprocessor extension.
Add a new debugging client, protocol, and adapter logic to
drive attach/launch, breakpoints, stepping, and evaluation
via the runtime adapter.

- Introduced a client debugger with a new adapter and protocol
- Wired attach/launch, breakpoints, stepping, and evaluation
- Updated docs and licensing to reflect the embedded debugger

client/src/debugger/protocol.js

@@ -0,0 +1,116 @@
+'use strict';
+
+const net = require('net');
+const { EventEmitter } = require('events');
+
+function encodeHex(value) {
+  return Buffer.from(String(value ?? ''), 'utf8').toString('hex') || '-';
+}
+
+function decodeHex(value) {
+  if (!value || value === '-') return '';
+  return Buffer.from(value, 'hex').toString('utf8');
+}
+
+class RuntimeConnection extends EventEmitter {
+  constructor() {
+    super();
+    this.socket = null;
+    this.buffer = '';
+    this.nextRequestId = 1;
+    this.pending = new Map();
+    this.closed = false;
+  }
+
+  connect(host, port) {
+    return new Promise((resolve, reject) => {
+      const socket = net.createConnection({ host, port });
+      const onError = (error) => {
+        socket.destroy();
+        reject(error);
+      };
+      socket.once('error', onError);
+      socket.once('connect', () => {
+        socket.removeListener('error', onError);
+        this.socket = socket;
+        this.closed = false;
+        socket.setEncoding('utf8');
+        socket.on('data', (chunk) => this.onData(chunk));
+        socket.on('error', (error) => this.emit('runtimeError', error));
+        socket.on('close', () => this.onClose());
+        resolve();
+      });
+    });
+  }
+
+  request(command, fields = [], timeoutMs = 30000) {
+    if (!this.socket || this.closed) {
+      return Promise.reject(new Error('NX runtime is not connected'));
+    }
+    const id = this.nextRequestId++;
+    const normalized = fields.map((field) => String(field ?? ''));
+    if (normalized.some((field) => field.includes('\t') || field.includes('\n'))) {
+      return Promise.reject(new Error('protocol fields must be hex-encoded before transmission'));
+    }
+
+    return new Promise((resolve, reject) => {
+      const timer = setTimeout(() => {
+        this.pending.delete(id);
+        reject(new Error(`NX ${command} request timed out`));
+      }, timeoutMs);
+      this.pending.set(id, { resolve, reject, timer, command });
+      this.socket.write(['REQ', id, command, ...normalized].join('\t') + '\n');
+    });
+  }
+
+  close() {
+    this.closed = true;
+    if (this.socket) this.socket.destroy();
+    this.socket = null;
+  }
+
+  onData(chunk) {
+    this.buffer += chunk;
+    let newline;
+    while ((newline = this.buffer.indexOf('\n')) >= 0) {
+      const line = this.buffer.slice(0, newline).replace(/\r$/, '');
+      this.buffer = this.buffer.slice(newline + 1);
+      if (line) this.onLine(line);
+    }
+  }
+
+  onLine(line) {
+    const fields = line.split('\t');
+    if (fields[0] === 'RES') {
+      const id = Number(fields[1]);
+      const pending = this.pending.get(id);
+      if (!pending) return;
+      this.pending.delete(id);
+      clearTimeout(pending.timer);
+      if (fields[2] === 'OK') {
+        pending.resolve({ command: fields[3], fields: fields.slice(4) });
+      } else {
+        pending.reject(new Error(decodeHex(fields[4]) || `NX ${pending.command} failed`));
+      }
+      return;
+    }
+    if (fields[0] === 'EVENT') {
+      this.emit('event', fields[1], fields.slice(2));
+      return;
+    }
+    this.emit('runtimeError', new Error(`unrecognized NX message: ${line}`));
+  }
+
+  onClose() {
+    if (this.closed) return;
+    this.closed = true;
+    for (const pending of this.pending.values()) {
+      clearTimeout(pending.timer);
+      pending.reject(new Error('NX runtime disconnected'));
+    }
+    this.pending.clear();
+    this.emit('close');
+  }
+}
+
+module.exports = { RuntimeConnection, encodeHex, decodeHex };