feat(setup)!: require Node 22.12+ and drop Node 20 (#152)

better-sqlite3 stopped publishing prebuilt binaries for Node 20's ABI
(115) in 12.10.0 - upstream, not a mirror gap:

    12.8.0 / 12.9.0   115 127 131 137 141
    12.10.0+              127 137 141 147

`better-sqlite3: ^12.8.0` resolves well past that, so every Node 20
install 404'd on the CDN, fell through to the source build, and demanded
Python plus a C++ toolchain before the bot could start at all. package.json
went on claiming `^20.19.0` worked, and the README went on recommending
Node 20 as one of two blessed versions. It was not a supported
configuration in any meaningful sense - it was a trap.

So say so up front: engines, both setup scripts, and the Docker images now
require Node 22.12+ (or 24+, which still needs a source build for opus).
The version gate in setup.bat / setup.sh is kept byte-identical to the
engines range, as before.

Also copy scripts/lib/console-log.mjs into the production image. The
previous commit had check-native.mjs import it, and the Dockerfile copies
check-native.mjs in on its own for `docker exec ... npm start` - without
its dependency that preflight now dies with ERR_MODULE_NOT_FOUND.

BREAKING CHANGE: Node 20 is no longer supported. Node 22.12 LTS or newer
is required; setup refuses to run on anything older.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

scripts/download-binaries.mjs

@@ -417,11 +417,12 @@ function buildFromSource(command) {
 /**
  * A 404 from the CDN is not a mirror outage: it means this exact package
  * version publishes no prebuilt binary for the running Node ABI at all.
- * better-sqlite3 dropped its Node 20 (ABI 115) builds in 12.10.0, and
- * @discordjs/opus 0.10.0 has none for Node 24 (ABI 137) - so a user on either
- * of those majors lands in the source-build fallback below and is told to
- * install Python and a C++ toolchain. Switching Node major is the far cheaper
- * fix, and nothing else in this output points at it. See issue #152.
+ * @discordjs/opus 0.10.0 has no build for Node 24 (ABI 137), so a user on that
+ * major lands in the source-build fallback below and is told to install Python
+ * and a C++ toolchain. Switching Node major is the far cheaper fix, and nothing
+ * else in this output points at it. (better-sqlite3 dropping its Node 20 / ABI
+ * 115 builds in 12.10.0 is why Node 20 is no longer accepted at all.)
+ * See issue #152.
  */
 function explainMissingPrebuild(name, version, err) {
   if (!/HTTP 404/.test(err.message)) return;
@@ -694,10 +695,9 @@ try {
   // that same loop. Run these concurrently and the first module to fall back to
   // a source build kills every download still in flight — the connection is
   // healthy, the timer just never got a chance to be reset. That is not a rare
-  // race: npmmirror has no opus prebuild for ABI 137 (Node 24) and no
-  // better-sqlite3 prebuild for ABI 115 (Node 20), so on both of the Node
-  // versions this project supports, one module 404s within ~100ms and starts
-  // building while ffmpeg's ~80MB download is still going. ffmpeg is optional,
+  // race: @discordjs/opus 0.10.0 has no prebuild for ABI 137, so on Node 24 that
+  // module 404s within ~100ms and starts building while ffmpeg's ~80MB download
+  // is still going. ffmpeg is optional,
   // so the spurious failure used to be swallowed as a WARN and setup still
   // reported success — leaving the user with no ffmpeg and no working playback.
   // Nothing here benefits from overlap anyway: every probe is execFileSync.