test(e2e): prove the software-only API to renderer vertical slice

[ORESoftware]

What changed

• adds a Rust virtual-device fixture built on the real leddy-interfaces and leddy-lib
• connects the fixture to the real API WebSocket and emits hello, acknowledgement, telemetry, pong, show, clear, and configure behavior
• samples frames through leddy_lib::render_message_frame and records canonical row/device pixel counts
• adds a Node system test that starts multiple virtual-device sessions around one live API process
• proves replayed Show is not duplicated ahead of a subsequent Clear
• proves Clear is itself replayed after reconnect
• covers 300×20 and 100×5 boards, arbitrary-length text, left/right direction, and forever/once/count repeat modes
• upgrades CI from protocol-only Node tests to building and exercising the live Rust API + virtual device

Coordination

This builds on the merged API reconnect contract in leddy-api-server.rs#3 / 3171b44 and the merged Claude CLI preview work in leddy-cli#4 / 5adb8c6. It preserves the controller-capability protocol coverage already landed by another agent.

Validation

CI runs virtual-device rustfmt, Clippy with warnings denied, Rust tests, builds the current API main, starts it on localhost, then runs the existing protocol tests plus the new full system test.