Companion module for the DiGiCo S31 with an iPad relay (v1)

Bitfocus Companion 5 connection module (ESM, @companion-module/base ~2.1.3,
runtime node22) for the DiGiCo S21/S31. It occupies the console's single
iPad slot, controls per-channel sends/assigns to one buss, aux send
level/on/pan, mutes, faders and snapshots, and relays any number of DiGiCo
iPad apps through to the console byte-for-byte.

The S31's iPad extension was probed live: it speaks the SD/DiGiCo Pad OSC
tree (console receives on 8000, replies only to the configured iPad port
9000). tools/mock-s31.js emulates the console and test/selftest.js runs the
link + relay end to end against it. docs/design-v2.md is the brief for the
generic v2 rewrite.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

README.md

@@ -0,0 +1,42 @@
+# companion-module-digico-s31
+
+Bitfocus Companion (5.0+) connection module for the DiGiCo S21/S31: per-channel control of
+one buss (the Apollo Beach "Studio" group by default), aux send level/on/pan, mutes, faders,
+snapshots — plus a UDP relay so several DiGiCo iPad apps can share the console's single iPad slot.
+
+User-facing documentation (console + iPad setup, variables, the verified protocol table) is in
+[companion/HELP.md](companion/HELP.md); Companion shows it on the connection's help button.
+
+## Layout
+
+| Path | Purpose |
+| --- | --- |
+| `src/main.js` | the `InstanceBase` subclass (config, lifecycle, state, learn log) |
+| `src/definitions.js` | actions, feedbacks, variables, presets |
+| `src/dialects.js` | address builders/parsers: `sd` (iPad extension, verified), `sseries` (OSC Control extension), `raw` |
+| `src/console-link.js` | one UDP socket to the console (fixed local port) |
+| `src/relay.js` | iPad relay: tracks clients, forwards verbatim, fans out |
+| `src/osc.js` | tolerant OSC codec |
+| `tools/` | `mock-s31.js` (console emulator, both dialects), `fake-ipad.js`, see `tools/README.md` |
+| `test/selftest.js` | end-to-end check: mock console ↔ link/relay ↔ fake iPad |
+
+## Develop
+
+```bash
+npm install          # @companion-module/base ~2.1.3 (2.2.x is rejected by Companion 5.0.x)
+npm test             # runs test/selftest.js against the mock console
+```
+
+## Install as a developer module (how it runs on AB-ProPresenter)
+
+1. Copy this folder, including `node_modules`, to the Companion computer, e.g.
+   `~/Apps/companion-dev-modules/companion-module-digico-s31/`.
+2. In the Companion launcher → Developer, enable developer modules and set the path to the
+   *parent* folder (`~/Apps/companion-dev-modules`); the launcher restarts Companion with
+   `--extra-module-path`. (On AB this was done by editing `dev_modules_path` in
+   `~/Library/Application Support/companion/config.json` and relaunching Companion.)
+3. Connections → Add → "DiGiCo: S21; S31" (version *Dev*). Later file changes hot-reload the
+   connection.
+
+The console side (Extensions → iPad) must point at the Companion computer's IP with
+Send Port 9000 / Receive Port 8000 (the module defaults).