stacks/fish-s2: build from dockerfile.dev — upstream has no plain Dockerfile

First fish-s2 deploy attempt failed in step 9/11:
  failed to read dockerfile: open dockerfile: no such file or directory

Upstream fishaudio/fish-speech ships:
  * dockerfile.dev  (lowercase, dev/test image)
  * compose.yml + compose.base.yml  (intended deploy path:
                                     `docker compose --profile server up`)

There is no standalone production Dockerfile. The dockerfile.dev
image is what their own compose.yml builds from anyway, so building
against it directly is functionally equivalent to using their compose
profile — we just keep our own restart-policy / labels / bind-mount
conventions on the outer compose.

Comment in the build block now documents this so future-Claude doesn't
re-walk the path.

stacks/fish-s2/compose.yaml

@@ -26,9 +26,16 @@ services:
     image: local/fish-s2:${FISH_S2_TAG}
     build:
       context: https://github.com/fishaudio/fish-speech.git#${FISH_S2_SHA}
-      dockerfile: dockerfile
+      # Upstream ships `dockerfile.dev` (lowercase, dev/test image)
+      # rather than a plain Dockerfile — there is no production
+      # Dockerfile. Their intended path is `docker compose --profile
+      # server up` against their own compose.yml; we use the same
+      # underlying dockerfile.dev image but layer our own compose on
+      # top so it slots into our fleet conventions (restart, labels,
+      # bind mounts, healthcheck).
+      dockerfile: dockerfile.dev
       args:
-        # Upstream's Dockerfile reads BACKEND to choose CUDA vs CPU
+        # Upstream's dockerfile.dev reads BACKEND to choose CUDA vs CPU
         # paths during pip install. We always want CUDA on irv-ml1.
         BACKEND: cuda
     container_name: fish-s2