fix(macos): don't intercept all devices when include/exclude list has no matches (#1986)

## Summary

- When `macos-dev-names-include` or `macos-dev-names-exclude` is
configured but no connected devices match, kanata was falling back to
`register_device("")` which intercepts **all** devices
- This caused kanata to grab the wrong keyboard (e.g., the internal
MacBook keyboard when an external keyboard was specified but not
connected)
- Now kanata only falls back to the catch-all registration when no
device filter is configured at all — when a filter is present but
nothing matches, kanata exits with an error

Fixes #1479

## Test plan

- [x] Configured `macos-dev-names-include` with a nonexistent device
name — kanata now errors out instead of grabbing all devices
- [x] Configured `macos-dev-names-include` with a real connected device
— kanata correctly grabs only that device and remapping works
- [x] No include/exclude list — default behavior unchanged (grabs all
devices)

## Possible follow-up

Linux has `linux-continue-if-no-devs-found` which lets kanata wait for
devices instead of exiting. A cross-platform `continue-if-no-devs-found`
option could be added to support the multi-instance use case where
kanata should stay running and pick up the device when it connects.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: malpern

src/oskbd/macos.rs

@@ -79,6 +79,7 @@ impl KbdIn {
 
         // Based on the definition of include and exclude names, they should never be used together.
         // Kanata config parser should probably enforce this.
+        let has_device_filter = include_names.is_some() || exclude_names.is_some();
         let device_names = if let Some(included_names) = include_names {
             validate_and_register_devices(included_names)
         } else if let Some(excluded_names) = exclude_names {
@@ -104,7 +105,10 @@ impl KbdIn {
             vec![]
         };
 
-        if !device_names.is_empty() || register_device("") {
+        // When an include/exclude list is configured but no devices matched,
+        // do NOT fall back to registering all devices. Only use the catch-all
+        // register_device("") when no device filter was specified at all.
+        if !device_names.is_empty() || (!has_device_filter && register_device("")) {
             if grab() {
                 Ok(Self { grabbed: true })
             } else {