feat: DevDesk v0.1.0, a persistent browser terminal for Claude Code

ttyd serves a single-file xterm.js UI styled with the LotusGuild TDS
(web_template base.css). Sessions live in a dedicated tmux server unit
(devdesk-tmux.service), so restarting or upgrading the web unit never
stops Claude. Each named session maps to a project directory. A Claude
SessionStart hook records the conversation ID, so after a reboot the
session resumes that exact conversation.

- bin/devdesk: attach / new / ls / end / pick, with an fzf picker
- ttyd requires a credential that NPM injects; origin check enabled
- debian/: dh 13 with --no-stop-on-upgrade for the tmux unit, bundled
  sha256-verified ttyd 1.7.7, lintian overrides, man page
- CI: lint, test, build, smoke-test, artifact; v* tags publish to the
  Gitea apt registry and create a release

Refs: tinker ticket 887531976

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/protocol.js

@@ -0,0 +1,106 @@
+// ttyd 1.7.x WebSocket protocol (see ttyd src/server.h and src/protocol.c).
+//
+// Frames are binary. The first message is a bare JSON object; every later
+// message starts with a one-character command.
+
+export const Client = Object.freeze({ INPUT: '0', RESIZE: '1', PAUSE: '2', RESUME: '3' });
+export const Server = Object.freeze({ OUTPUT: '0', SET_WINDOW_TITLE: '1', SET_PREFERENCES: '2' });
+
+export const SESSION_RE = /^[A-Za-z0-9][A-Za-z0-9_-]{0,63}$/;
+export const LIST_ARG = '--list';
+
+const encoder = new TextEncoder();
+
+export function encodeInit(token, columns, rows) {
+  return encoder.encode(JSON.stringify({ AuthToken: token, columns, rows }));
+}
+
+export function encodeInput(text) {
+  const body = encoder.encode(text);
+  const frame = new Uint8Array(body.length + 1);
+  frame[0] = Client.INPUT.charCodeAt(0);
+  frame.set(body, 1);
+  return frame;
+}
+
+// xterm.js onBinary delivers a "binary string" (one char per byte).
+export function encodeBinaryInput(binary) {
+  const frame = new Uint8Array(binary.length + 1);
+  frame[0] = Client.INPUT.charCodeAt(0);
+  for (let i = 0; i < binary.length; i++) frame[i + 1] = binary.charCodeAt(i) & 0xff;
+  return frame;
+}
+
+export function encodeResize(columns, rows) {
+  return encoder.encode(Client.RESIZE + JSON.stringify({ columns, rows }));
+}
+
+export function encodeCommand(command) {
+  return encoder.encode(command);
+}
+
+export function decodeServer(data) {
+  const bytes = new Uint8Array(data);
+  return { type: String.fromCharCode(bytes[0]), payload: bytes.subarray(1) };
+}
+
+// URLs are relative to the page so DevDesk also works under a path prefix.
+function basePath(location) {
+  return location.pathname.replace(/[^/]*$/, '');
+}
+
+export function tokenUrl(location) {
+  return `${location.protocol}//${location.host}${basePath(location)}token`;
+}
+
+export function wsUrl(location, arg) {
+  const scheme = location.protocol === 'https:' ? 'wss:' : 'ws:';
+  const query = arg ? `?arg=${encodeURIComponent(arg)}` : '';
+  return `${scheme}//${location.host}${basePath(location)}ws${query}`;
+}
+
+export function sessionFromSearch(search) {
+  const value = new URLSearchParams(search).get('arg');
+  return value && SESSION_RE.test(value) ? value : null;
+}
+
+// tmux set-titles-string is "devdesk:#S|#T"; the picker prints "devdesk:picker|…".
+export function parseTitle(title) {
+  const match = /^devdesk:([^|]*)\|([\s\S]*)$/.exec(title || '');
+  if (!match) return null;
+  return { session: match[1], pane: match[2] };
+}
+
+// Output of `devdesk attach --list` arrives through a pty: CRLF line endings and
+// possibly split across frames. Pull the JSON object out of the joined text.
+export function parseListOutput(raw) {
+  // eslint-disable-next-line no-control-regex
+  const text = raw.replace(/\x1b\[[0-9;?]*[ -/]*[@-~]/g, ''); // tools may colorize on a tty
+  const start = text.indexOf('{');
+  const end = text.lastIndexOf('}');
+  if (start < 0 || end < start) throw new Error('no session list in output');
+  return JSON.parse(text.slice(start, end + 1));
+}
+
+// Same back-pressure scheme as ttyd's own client: pause the pty when xterm.js
+// falls behind on rendering, resume once it catches up.
+export class FlowControl {
+  constructor({ limit = 100000, highWater = 10, lowWater = 4 } = {}) {
+    Object.assign(this, { limit, highWater, lowWater, written: 0, pending: 0 });
+  }
+
+  // Returns { command, track }: command is PAUSE when the writer should stop;
+  // track says whether to pass a callback to term.write (and call release()).
+  onData(length) {
+    this.written += length;
+    if (this.written <= this.limit) return { command: null, track: false };
+    this.written = 0;
+    this.pending += 1;
+    return { command: this.pending > this.highWater ? Client.PAUSE : null, track: true };
+  }
+
+  release() {
+    this.pending = Math.max(this.pending - 1, 0);
+    return this.pending < this.lowWater ? Client.RESUME : null;
+  }
+}