tools/dev-deploy: log the sandbox-cancellation TODO

Capture the diagnostic notes for the issue we hit after every
`dev-deploy.yaml` redispatch: the freshly-bootstrapped "Dev Sandbox"
game ends up `cancelled` ~15 minutes later, with the runtime
reconciler reporting "container disappeared". The engine never
shows up in `docker ps -a --filter label=galaxy-game-engine`, so
either it never spawned or it was removed before any host-side
snapshot.

`KNOWN-ISSUES.md` records the symptom, the log excerpt, three
working hypotheses (runtime spawn race, `--remove-orphans`
interaction, engine `--rm` lifecycle), and the investigation
checklist before opening an issue. The README gets a one-line
pointer so future redeploys land on the doc immediately.

No code change — this is the placeholder so the next person
investigating the cancellation pattern does not have to
rediscover the diagnostic from scratch.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tools/dev-deploy/README.md

@@ -177,6 +177,12 @@ make clean-data     Stop everything and wipe volumes + game-state dir
 - `.env.example` — non-secret defaults for the compose `${VAR:-}`
   expansions. Copy to `.env` if you want host-local overrides.
 
+## Known issues
+
+See [`KNOWN-ISSUES.md`](KNOWN-ISSUES.md) for symptoms that surface
+in the long-lived dev environment but are not yet fixed (currently:
+the sandbox game flipping to `cancelled` after a redispatch).
+
 ## Relationship to other infrastructure
 
 - `tools/local-dev/` — single-developer playground, host-port mapped,