streamdeck_connect always grabs the first enumerated device — no way to target a specific deck when multiple are attached

[bandrel]

Problem

server.py:292 hardcodes self.deck = decks[0], so when more than one Stream Deck is connected (e.g. an Original and a Plus on the same machine), the MCP can only ever talk to whichever device DeviceManager().enumerate() returns first. There is no tool argument to choose, and no list_devices tool to discover what's attached.

Repro on a machine with two decks plugged in:

streamdeck_connect  →  always opens the same one regardless of intent

Suggested fix

Two small additions:

1. New tool streamdeck_list_devices — enumerate without opening, return [{serial, deck_type, key_count}, ...]. No connection required, safe to call any time.
2. Optional arg on streamdeck_connect — serial: str | None = None. If provided, match against enumerated devices; if not, keep current behavior (open first). On a non-matching serial, error with the list of available serials so the caller can self-correct.

Sketch:

def connect(self, serial: str | None = None) -> dict[str, Any]:
    ...
    decks = DeviceManager().enumerate()
    if not decks:
        raise StreamDeckError("No Stream Deck found...")

    if serial is None:
        self.deck = decks[0]
    else:
        match = next((d for d in decks if d.get_serial_number() == serial), None)
        if match is None:
            available = [d.get_serial_number() for d in decks]
            raise StreamDeckError(f"No deck with serial {serial!r}. Available: {available}")
        self.deck = match
    ...

Out of scope (worth noting, not solving here)

State persistence (~/.streamdeck-mcp/pages.json, buttons.json) is currently global. True multi-deck support eventually wants per-serial state files, but that's a larger change — selecting which deck to open is the prerequisite and useful on its own.