D7 chain-by-default, delivered with minimal player surgery:
- ReaderMetadata gains PodcastSequence: the neighboring DOWNLOADED
episodes in the caller's effective order (D5 override applied,
feed-native fallback; computed in the reader route for
source='podcast_episode' items — RLS already scoped the reads; gaps
never enter the chain, invariant 6). ?single=1 escapes chaining (the
'play single episode' affordance).
- Audio reader renders the sequence into body[data-json]
(AudioReaderConfigJSON — books produce the identical shape minus the
sequence key, so the reader path is unchanged for them) and an
'Ep N/M' indicator + prev/next episode controls in the header.
- audio.ts: the last-track 'ended' handler chains into the next
episode's reader page (final progress push precedes navigation);
back button exits episodes to their feed page. Books are untouched —
no sequence context, zero behavior change. Day-one chaining is
page-navigation based (progress persists; position restores).
Continue aggregation (2.5): GetPodcastContinueForUser (in-progress
episodes, most-recent-first, ≥95% excluded) feeds a Continue section
on /podcasts — sorted most recently listened, cards show 'Ep N · title'
— ahead of All Feeds. Cards prefer the continue line over the
description.