feat(booth): downloadable booths — whole-booth zip + ?dl force-download (v0.1.4)

A verbatim index.html booth (e.g. edict-design-brief: a rendered brief + its
.md) had no download affordance — the page is served raw with no gallery/per-file
chrome. Adds:
  - GET /b/<name>/?download=1 -> streams the whole booth as <name>.zip (attachment)
  - GET /b/<name>/<file>?dl=1 -> forces Content-Disposition: attachment (html/md/
    text otherwise render inline with no easy save)
  - a download link on the index card (the accessible spot for verbatim booths)
    and the gallery header
Tests for both; verified live against edict-design-brief on nh3-dev :8090.

booth/app.py

@@ -17,10 +17,12 @@ State is the filesystem — `ls ~/booth-data` tells you everything. That is the
 from __future__ import annotations
 
 import asyncio
+import io
 import os
 import secrets
 import shutil
 import time
+import zipfile
 from contextlib import asynccontextmanager
 from pathlib import Path
 from urllib.parse import quote
@@ -31,6 +33,7 @@ from fastapi.responses import (
     HTMLResponse,
     JSONResponse,
     RedirectResponse,
+    Response,
 )
 from fastapi.templating import Jinja2Templates
 
@@ -206,6 +209,27 @@ def build_gallery(child: Path) -> list[dict]:
     return items
 
 
+def zip_booth(booth: Path) -> bytes:
+    """Zip a booth's whole tree (dotfiles excluded) into an in-memory archive.
+
+    Lets a booth be downloaded as one artifact regardless of shape — the case a
+    verbatim `index.html` booth (e.g. a rendered brief + its assets) has no
+    per-file download affordance for, since the page is served raw.
+    """
+    buf = io.BytesIO()
+    with zipfile.ZipFile(buf, "w", zipfile.ZIP_DEFLATED) as zf:
+        for p in sorted(booth.rglob("*")):
+            if p.is_file() and not p.name.startswith("."):
+                zf.write(p, p.relative_to(booth).as_posix())
+    return buf.getvalue()
+
+
+def _zip_filename(name: str) -> str:
+    """A Content-Disposition-safe `<booth>.zip` (strip quotes/control chars)."""
+    safe = "".join(c for c in name if c.isprintable() and c != '"')
+    return f"{safe or 'booth'}.zip"
+
+
 # ---- uploads (browser drop-off for pickup) ---------------------------------
 
 UPLOAD_MARKER = ".uploaded"  # dotfile stamped into upload booths (excluded from listings)
@@ -331,8 +355,16 @@ def create_app(
         return RedirectResponse(url=f"/b/{quote(name, safe='')}/", status_code=307)
 
     @app.get("/b/{name}/", response_class=HTMLResponse)
-    def booth_view(request: Request, name: str):
+    def booth_view(request: Request, name: str, download: int = 0):
         booth = resolve_booth(name)
+        if download:
+            # whole-booth zip — the download path for a verbatim index.html booth
+            # (which has no gallery/per-file chrome), and a "download all" for any.
+            return Response(
+                content=zip_booth(booth),
+                media_type="application/zip",
+                headers={"Content-Disposition": f'attachment; filename="{_zip_filename(name)}"'},
+            )
         own_index = booth / "index.html"
         if own_index.is_file():
             return FileResponse(str(own_index), media_type="text/html")
@@ -375,7 +407,7 @@ def create_app(
         )
 
     @app.get("/b/{name}/{filepath:path}")
-    def booth_file(name: str, filepath: str):
+    def booth_file(name: str, filepath: str, dl: int = 0):
         booth = resolve_booth(name)
         try:
             target = (booth / filepath).resolve()
@@ -383,6 +415,11 @@ def create_app(
             raise HTTPException(status_code=404, detail="no such file")
         if not str(target).startswith(str(booth) + os.sep) or not target.is_file():
             raise HTTPException(status_code=404, detail="no such file")
+        # ?dl=1 forces a download (Content-Disposition: attachment) instead of the
+        # browser rendering inline — the fix for html/md/text that otherwise opens
+        # in-page with no easy "save".
+        if dl:
+            return FileResponse(str(target), filename=target.name)
         return FileResponse(str(target))
 
     @app.post("/upload")