v26.5.0-alpha.8

mdl v26.5.0-alpha.8 - circuit watch subscriptions and change events

Adds event-driven redstone circuit observation on top of the v26.11
circuit query and the alpha.5/6 orchestration watcher.

Agent API:
POST /game/:instance/watch
Register an in-memory named cube watch:
{"name":"door","x":-516,"y":71,"z":-87,"radius":3}
Radius 1-8 (default 4); coordinates are required.
GET /game/:instance/watch
List watches.
DELETE /game/:instance/watch/:name
Remove a watch.

Watches never modify the game and intentionally vanish on agent server
restart. The watcher only polls watches for instances tracked by this
agent server, so cost is bounded by live games.

WorldProbes.circuit response shape is pinned from Despotes source and
locked by tests. Components are diffed by position; circuit_changed
events report appeared/changed/removed components when block/powered/
delay/note/facing/locked state changes. Detail lists cap at 64 entries
with a truncated marker.

Menu screens (inWorld=false) preserve the prior scan instead of
creating mass removals. Deleting a watch clears its snapshot so
re-registering the same name receives a fresh first scan.

Live API lifecycle verified: register, list, duplicate=409, remove,
list-empty. Tests: 28 lib + 190 bin, zero warnings.

Instability disclaimer: alpha pre-release - expect rough edges.