feat(podcasts): real-time episode list — byte progress bars, direct swaps (issues #1/#3)

WHY: downloads needed manual refreshes to see progress; the 204 +
HX-Trigger event indirection missed its listener, and the worker
buffered whole enclosures so no progress existed to show.

- Worker streams enclosures to disk through a counting loop (64KiB
  chunks, scheme/redirect/size guards preserved) with an in-memory
  per-episode progress snapshot (received/total; total from
  Content-Length, seeded by the feed's declared length). Deliberately
  transient — the DB row state remains the durable truth.
- Episode-list renderer seam: the router injects a closure into
  PodcastHandler (handlers can't import templates — MediaDetail cycle)
  so htmx download/retry/Download All/refresh/order/policy actions
  answer with the REFRESHED partial directly (200, hx-target=
  #episode-list) — no events to miss. Non-HX callers keep JSON; tests
  without a renderer keep 204+trigger.
- Polling tightens to 2s while downloads are active; downloading rows
  render a percentage bar + MB counter (quote-free inline style per
  templ gotcha #8) or an indeterminate bar when the server sends no
  length.
- Issue #3: Download All (button AND the add-feed checkbox) flips the
  CALLER's subscription policy to 'all' — per-user, never global (D6:
  files shared, policies not) — and the auto-download select
  out-of-band-swaps so the dropdown shows what the user is getting.
  They can turn it down afterwards; the flip is honest communication,
  not coercion (user-approved 2026-10-29).

PINs: Download All with HX answers 200 + episode-list + oob select and
flips newest → all; add-feed download_all sets policy all.

web/src/podcasts.ts

@@ -18,10 +18,11 @@ Alpine.data("podcastsPage", () => ({
   },
 }));
 
-// The detail page's actions are pure htmx (hx-post/hx-put/hx-delete +
-// HX-Trigger-driven list refresh); Alpine only hosts the x-data the
-// body declares so CSP-bound Alpine stays happy.
-Alpine.data("podcastDetail", () => ({}));
+// The detail page's actions are pure htmx; Alpine hosts the x-data the
+// body declares (modal visibility) so CSP-bound Alpine stays happy.
+Alpine.data("podcastDetail", () => ({
+  unsubOpen: false,
+}));
 
 // Add-feed form: surface the server's error text inline (the JSON error
 // body arrives on non-2xx; htmx swaps nothing). Success redirects via