Merge pull request 'Module rules: a native helper ships prebuilt, for Apple silicon and Windows' (#35) from claude/module-helper-rules into main

The machine running ProdDash is a packaged app or the Windows bundle plus
modules from the admin page's catalog. It has no compiler, and the catalog
delivers exactly the folder that is in the repo — so a module's native
program (audio capture, a decoder) ships already built, inside the module
folder, one file per platform: bin/<name>-macos-arm64 and
bin/<name>-win-x64.exe are required, Intel macOS optional, source and the
script that rebuilds every binary under native/.

The guide's rule 3 now says so, "The shape of a module" shows the layout,
and a new "Native helpers" section gives the contract: pick the binary by
platform at runtime, report the feature off when there is none — never
build, never search the machine, never ask the operator to install
anything — one command-line contract in any language per platform, bump
the version when a binary changes, keep them lean, sign the macOS one.
CLAUDE.md carries the one-line version. Rules only: no module changes here.

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

CLAUDE.md

@@ -28,7 +28,12 @@ title-bar controls). The rules that matter most:
   ship inside the module folder** (zero deps is the norm). **Everything the
   module does runs inside its server entry** — no helper scripts, companion
   programs or daemons the operator starts by hand; a listener or decoder is
-  started in `init()` and stopped in `stop()`. Declare `"proddash": ">=x.y.z"`
+  started in `init()` and stopped in `stop()`. **A native helper ships
+  prebuilt inside the module folder for Apple silicon macOS and 64-bit
+  Windows** (`bin/<name>-macos-arm64`, `bin/<name>-win-x64.exe`, source and
+  build script under `native/`); nothing is ever compiled on the machine
+  running ProdDash, and a missing binary means the feature reports itself
+  off, not a broken module. Declare `"proddash": ">=x.y.z"`
   and bump the module's `version` on every change.
 - Browsers never call upstream services directly; the module's server routes
   proxy everything (no CORS, secrets stay server-side).

docs/MODULE-GUIDE.md

@@ -28,7 +28,10 @@ people running the booth depend on them.
    ProdDash. If your feature needs a listener, a decoder or a worker, your
    server entry owns it: start it in `init()`, stop it in `stop()`, report
    it in `health()`. A child process the module itself spawns and supervises
-   is fine; a program someone launches by hand is not.
+   is fine; a program someone launches by hand is not. **A native helper —
+   anything that is not JavaScript — ships prebuilt inside the module folder,
+   for Apple silicon macOS and 64-bit Windows; nothing is ever compiled on
+   the machine running ProdDash** (see "Native helpers" below).
 4. **Declare the ProdDash version you need** (`"proddash": ">=1.1.0"` in the
    manifest) and **bump your own `version`** whenever you change the module.
    The admin page refuses to install a module whose requirement the running
@@ -83,6 +86,10 @@ modules/<id>/
 ├── module.json      manifest (required)
 ├── client.js        ES module, client entry (required)
 ├── server.js        server entry (optional — only if you need server code)
+├── bin/             native helpers, prebuilt per platform (only if you need one)
+│   ├── <name>-macos-arm64
+│   └── <name>-win-x64.exe
+├── native/          their source and the script that builds every bin/ file
 └── ... assets       (css, images…) served statically at /modules/<id>/
 ```
 
@@ -97,6 +104,66 @@ the newer version runs. **Uninstall** in the admin page removes an installed
 module's files (a bundled one is hidden instead, since its folder belongs to
 the app); its settings are kept for a later reinstall.
 
+### Native helpers
+
+Some features need a program JavaScript cannot be: reading an audio input,
+decoding timecode, measuring sound. Rule 3 says the module owns that program;
+this section says how it ships: **already built, for every platform it runs
+on, inside the module folder.** The machine running ProdDash is a packaged
+app or the Windows bundle plus modules from the admin page's catalog. It has
+no compiler and never will — the catalog delivers exactly the folder that is
+in the repo, so the binaries live in git next to the code.
+
+- **Platforms.** Apple silicon macOS and 64-bit Windows are required. Intel
+  macOS is welcome but optional. One file per platform in `bin/`, named for
+  what it is:
+
+  | Platform | File |
+  | --- | --- |
+  | macOS, Apple silicon | `bin/<name>-macos-arm64` |
+  | Windows, 64-bit | `bin/<name>-win-x64.exe` |
+  | macOS, Intel (optional) | `bin/<name>-macos-x86_64` |
+
+- **Pick it at runtime, and cope without it.** Choose by `process.platform`
+  and `process.arch`; when there is no file for this machine, the feature
+  says so — in `health()` and in the tile's `setStatus` — and everything else
+  in the module keeps working. Never try to build it, never look for a copy
+  elsewhere on the machine, never tell the operator to install anything.
+
+  ```js
+  const HELPERS = {
+    darwin: { arm64: 'ltc-capture-macos-arm64', x64: 'ltc-capture-macos-x86_64' },
+    win32: { x64: 'ltc-capture-win-x64.exe' },
+  };
+  const name = HELPERS[process.platform]?.[process.arch];
+  const helper = name ? path.join(__dirname, 'bin', name) : '';
+  if (!helper || !fs.existsSync(helper)) {
+    // Timecode is off on this platform. Say it once, keep the clock running.
+  }
+  ```
+
+- **One contract, any language.** Every platform's binary speaks the same
+  command line and output format, so `server.js` has one code path. What is
+  behind it is your choice per platform — Swift against CoreAudio on macOS,
+  C#, C or Rust on Windows — the module does not care.
+- **Source and build beside it.** Keep the source under `native/` with one
+  script that produces every `bin/` file from a checkout, so any binary can be
+  rebuilt from what is committed. A helper that cannot be rebuilt does not
+  ship.
+- **Bump the module version whenever a binary changes**, like any other
+  file — that is how installs learn about it.
+- **Keep them lean.** Optimised builds, no debug symbols, a few megabytes at
+  most: the catalog fetches the whole repo as one archive, capped at 80 MB.
+- **Signing.** Apple silicon refuses unsigned code, so sign the macOS binary
+  — Developer ID when you have it, ad-hoc at least. Windows needs nothing:
+  files the app writes carry no download mark, so SmartScreen never sees
+  them. Permissions come from the launcher (see "Permissions macOS has to
+  grant"), not from the binary.
+
+A helper that ends up existing for one platform only is an exception made
+on purpose, not a default: say so in the module's README and in the health
+line, so a Windows booth knows why the feature is off.
+
 ## module.json
 
 ```json