Add Gitea Actions CI/CD workflow for pack build and release

Builds the client pack on the media-server docker runner: refreshes the
packwiz index, runs integrity + download-resolvability checks, exports
Modrinth (.mrpack) and CurseForge (.zip) artifacts, validates the
CurseForge manifest completeness, uploads artifacts, and publishes a
release on v* tags.

.gitea/workflows/build-pack.yaml

@@ -0,0 +1,146 @@
+name: Build & Release Pack
+
+on:
+  push:
+    branches: [main]
+    tags: ['v*']
+
+jobs:
+  build:
+    runs-on: docker
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '1.22'
+
+      - name: Install packwiz
+        run: go install github.com/packwiz/packwiz@latest
+
+      - name: Add packwiz to PATH
+        run: echo "$(go env GOPATH)/bin" >> "$GITHUB_PATH"
+
+      - name: Refresh index
+        working-directory: client_pack
+        run: packwiz refresh
+
+      - name: Integrity check
+        working-directory: client_pack
+        run: |
+          python3 - <<'EOF'
+          import hashlib, os, re, sys, tomllib
+          index = tomllib.load(open("index.toml", "rb"))
+          indexed = {e["file"] for e in index["files"]}
+          mods = [f for f in os.listdir("mods") if f.endswith(".pw.toml")]
+          missing = [f for f in mods if f"mods/{f}" not in indexed]
+          if missing:
+              print("ERROR: pw.toml files missing from index.toml:", missing)
+              sys.exit(1)
+          extra = [f for f in indexed if f.startswith("mods/") and f not in {f"mods/{m}" for m in mods}]
+          if extra:
+              print("ERROR: index.toml entries missing from mods/:", extra)
+              sys.exit(1)
+          errors = 0
+          for f in mods:
+              data = tomllib.load(open(f"mods/{f}", "rb"))
+              d = data.get("download")
+              if not d or not d.get("hash"):
+                  print(f"ERROR: {f} missing [download] hash")
+                  errors += 1
+                  continue
+              if not d.get("url") and not d.get("mode", "").startswith("metadata:"):
+                  print(f"ERROR: {f} missing [download] url or metadata mode")
+                  errors += 1
+              if d.get("url", "").startswith("http://"):
+                  print(f"ERROR: {f} uses insecure http url")
+                  errors += 1
+              hf = d.get("hash-format", "sha512")
+              if not re.fullmatch(r"[0-9a-f]+", d["hash"]):
+                  print(f"ERROR: {f} hash not hex ({hf})")
+                  errors += 1
+          if errors:
+              sys.exit(1)
+          print(f"OK: {len(mods)} mods indexed, all have [download] url or metadata source")
+          EOF
+
+      - name: Sanity grep download URLs
+        working-directory: client_pack
+        run: |
+          python3 - <<'EOF'
+          import glob, sys, tomllib
+          bad = []
+          url_count = 0
+          meta_count = 0
+          for f in sorted(glob.glob("mods/*.pw.toml")):
+              d = tomllib.load(open(f, "rb")).get("download", {})
+              if d.get("url"):
+                  url_count += 1
+              elif d.get("mode", "").startswith("metadata:"):
+                  meta_count += 1
+              else:
+                  bad.append(f)
+          if bad:
+              print("ERROR: mods without download.url or metadata mode:")
+              for f in bad:
+                  print("  " + f)
+              sys.exit(1)
+          print(f"OK: {url_count} direct urls + {meta_count} metadata sources = all mods resolvable")
+          EOF
+
+      - name: Export Modrinth pack
+        working-directory: client_pack
+        run: packwiz modrinth export -o ../SciCraft-Modrinth.mrpack --restrictDomains=false
+
+      - name: Export CurseForge pack
+        working-directory: client_pack
+        run: packwiz curseforge export -o ../SciCraft-CurseForge.zip
+
+      - name: Validate CurseForge pack completeness
+        working-directory: client_pack
+        run: |
+          python3 - <<'EOF'
+          import json, os, re, sys, zipfile, tomllib
+          z = zipfile.ZipFile("../SciCraft-CurseForge.zip")
+          manifest = json.loads(z.read("manifest.json"))
+          pids = {f["projectID"] for f in manifest["files"]}
+          ov = {n.split("overrides/mods/")[1] for n in z.namelist() if n.startswith("overrides/mods/")}
+          missing = []
+          for f in os.listdir("mods"):
+              if not f.endswith(".pw.toml"):
+                  continue
+              data = tomllib.load(open(f"mods/{f}", "rb"))
+              if data.get("side") == "server":
+                  continue
+              fn = data["filename"]
+              cf = data.get("update", {}).get("curseforge", {}).get("project-id")
+              if cf:
+                  if cf not in pids:
+                      missing.append(fn)
+              elif fn not in ov:
+                  missing.append(fn)
+          if missing:
+              print("ERROR: mods missing from CurseForge export:", missing)
+              sys.exit(1)
+          print(f"OK: CurseForge export complete ({len(pids)} manifest files + {len(ov)} overrides)")
+          EOF
+
+      - name: Upload pack artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          name: scicraft-pack
+          path: |
+            SciCraft-Modrinth.mrpack
+            SciCraft-CurseForge.zip
+
+      - name: Release
+        if: startsWith(github.ref, 'refs/tags/v')
+        uses: softprops/action-gh-release@v1
+        with:
+          files: |
+            SciCraft-Modrinth.mrpack
+            SciCraft-CurseForge.zip
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}