refactor(macos): Improve solaar executable lookup in launchagent script

This change improves how the `create-macos-launchagent.sh` script locates the `solaar` executable.

Previously, the script defaulted to a hardcoded path (`/opt/homebrew/bin/solaar`) and would exit with an error if that specific file was not found and executable. This was too restrictive and failed in environments where `solaar` is installed in a different location, such as through `pipx` or in standard system paths like `/usr/local/bin`.

Now, the script defaults the `SOLAAR_PATH` to just `solaar` and uses the `command -v` utility to find the executable in the user's `PATH`. This allows the system to resolve the correct location of the `solaar` binary automatically. If the executable cannot be found in the `PATH`, the script now issues a warning instead of exiting, and proceeds to use the provided `SOLAAR_PATH` value in the generated LaunchAgent plist. This makes the script more flexible and robust for different installation methods.

tools/create-macos-launchagent.sh

@@ -28,7 +28,7 @@ cat > "${LAUNCH_AGENT_PLIST}" <<EOF
     <string>io.github.pwr-solaar.solaar</string>
     <key>ProgramArguments</key>
     <array>
-        <string>${SOLAAR_PATH}</string>
+        <string>${SOLAAR_RESOLVED_PATH}</string>
         <string>--window=hide</string>
     </array>
     <key>RunAtLoad</key>