fix(docker): install jsonschema and copy schemas/ into the image

[dmccoystephenson]

The image never ran

The Dockerfile (added in #113 for containerized deployment) installs no dependencies, on the stated premise that the game is stdlib-only. That premise is false — src/fishE.py imports jsonschema at module scope, so the game cannot start without it:

• src/fishE.py:3 — from jsonschema.exceptions import ValidationError
• src/validation/schemaValidator.py:4 — from jsonschema import validate

This was caught when the image was deployed for real for the first time (behind fishe.danielstephenson.dev). The container crash-looped 638 times before it was pulled:

File "/app/examples/../src/fishE.py", line 3, in <module>
  from jsonschema.exceptions import ValidationError
ModuleNotFoundError: No module named 'jsonschema'

The dependency was recorded in exactly one place — .github/workflows/test.yml's pip install pytest pytest-cov jsonschema pygame. There's no requirements.txt, and run.sh's checkDependencies() (which would have installed one) is commented out, so nothing propagated it to the image.

A second, latent bug behind the first

Fixing only the import would have moved the failure rather than removed it. The save-file readers resolve their schemas relative to the process cwd:

PLAYER_SCHEMA_PATH = "schemas/player.json"   # playerJsonReaderWriter.py:5

cwd is /app in the image, and schemas/ was never copied in — so every save load/write would have raised FileNotFoundError. The app would have started, served the menu, and then broken the moment a player touched a save slot.

Changes

• requirements.txt (new) — jsonschema>=4.0,<5.0. pygame is deliberately excluded: the pygame front-end imports it lazily, so the console and web front-ends run without it.
• Dockerfile — install from requirements.txt, copy schemas/, and drop the inaccurate "no third-party deps" comment.

Verification

Reproduced and fixed against the exact file layout each Dockerfile produces, using a clean venv with no jsonschema:

	old layout	fixed layout
python3 examples/web_app.py	ModuleNotFoundError: No module named 'jsonschema'	starts, serves in ~1s
GET /	—	200, contains <title>FishE</title>
GET /state	—	200, JSON with screen/version
validate_against_schema({}, PLAYER_SCHEMA_PATH)	FileNotFoundError: schemas/player.json	schema loads (raises ValidationError, as expected for {})

The GET / check is the exact command the gateway healthcheck runs.

No src/ changes, so the existing test suite is unaffected — CI installs jsonschema explicitly and is independent of the new requirements.txt.