feat: add compatibility table endpoint and rendering for game libraries

ams/api/routes/compat.py

@@ -0,0 +1,49 @@
+"""Catalog-wide compatibility table, grouped by library name, as a downloadable file.
+
+    GET /compat?format=md    -> Markdown table (attachment compat.md)
+    GET /compat?format=json  -> structured JSON (attachment compat.json)
+
+Builds `ams.compat` entries from every catalogued snapshot, labelling each by its game (or
+'(bez gry)' when unlinked). Same engine library name across games clusters into surface variants,
+so divergent copies get an asterisk — exactly what the docs table needs.
+"""
+
+from __future__ import annotations
+
+from fastapi import APIRouter, Depends, Query
+from fastapi.responses import Response
+from sqlalchemy import select
+from sqlalchemy.orm import Session
+
+from ...compat import Entry, compatibility_table, render_json, render_markdown
+from ...snapshot import Snapshot as Surface
+from .. import models
+from ..db import get_db
+
+router = APIRouter(tags=["compat"])
+
+_NO_GAME = "(bez gry)"
+
+
+@router.get("/compat")
+def get_compat(
+    format: str = Query("md", pattern="^(md|json)$", description="md = Markdown, json = structured"),
+    db: Session = Depends(get_db),
+) -> Response:
+    entries = [
+        Entry(game=snap.game.name if snap.game else _NO_GAME, snapshot=Surface(snap.data))
+        for snap in db.scalars(select(models.Snapshot).order_by(models.Snapshot.id))
+    ]
+    table = compatibility_table(entries)
+
+    if format == "json":
+        return Response(
+            content=render_json(table),
+            media_type="application/json",
+            headers={"Content-Disposition": 'attachment; filename="compat.json"'},
+        )
+    return Response(
+        content=render_markdown(table),
+        media_type="text/markdown; charset=utf-8",
+        headers={"Content-Disposition": 'attachment; filename="compat.md"'},
+    )