feat: add workflow to generate schema diagram and update README

scripts/generate-schema-diagram.sh

@@ -0,0 +1,61 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+repo_root="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+schema_sql="$repo_root/ops/0.schema.sql"
+out_dir="$repo_root/.github/image"
+
+tmp_dir="$(mktemp -d)"
+dot_file="$tmp_dir/schema.dot"
+
+SCHEMA_SQL="$schema_sql" DOT_FILE="$dot_file" python3 - <<'PY'
+import os
+import re
+from pathlib import Path
+
+schema_sql = Path(os.environ["SCHEMA_SQL"]).read_text(encoding="utf-8")
+
+create_table_re = re.compile(r"CREATE\s+TABLE\s+([A-Za-z0-9_]+)\s*\(", re.IGNORECASE)
+references_re = re.compile(r"REFERENCES\s+([A-Za-z0-9_]+)", re.IGNORECASE)
+
+tables = set(create_table_re.findall(schema_sql))
+blocks = re.split(r"CREATE\s+TABLE\s+", schema_sql, flags=re.IGNORECASE)[1:]
+
+edges = set()
+for block in blocks:
+    name_match = re.match(r"([A-Za-z0-9_]+)", block)
+    if not name_match:
+        continue
+    table_name = name_match.group(1)
+    for ref in references_re.findall(block):
+        edges.add((table_name, ref))
+
+lines = []
+lines.append("digraph schema {")
+lines.append("  rankdir=LR;")
+lines.append("  splines=true;")
+lines.append("  overlap=false;")
+lines.append("")
+for table in sorted(tables):
+    lines.append(f'  "{table}";')
+lines.append("")
+for src, dst in sorted(edges):
+    lines.append(f'  "{src}" -> "{dst}";')
+lines.append("}")
+
+Path(os.environ["DOT_FILE"]).write_text("\n".join(lines) + "\n", encoding="utf-8")
+PY
+
+mkdir -p "$out_dir"
+
+dot -Tsvg -o "$out_dir/schema.svg" \
+  -Gbgcolor="#ffffff" \
+  -Nshape="box" -Nstyle="filled" -Nfillcolor="#f8f8f8" -Ncolor="#444444" -Nfontcolor="#111111" -Nfontname="Helvetica" -Nfontsize="12" \
+  -Ecolor="#666666" \
+  "$dot_file"
+
+dot -Tsvg -o "$out_dir/schema-dark.svg" \
+  -Gbgcolor="#0b0b0b" \
+  -Nshape="box" -Nstyle="filled" -Nfillcolor="#1f1f1f" -Ncolor="#777777" -Nfontcolor="#f5f5f5" -Nfontname="Helvetica" -Nfontsize="12" \
+  -Ecolor="#aaaaaa" \
+  "$dot_file"