[KodeStar]

Docs for Bridge Phase 2c-2b, on-demand podcast play. Pairs with KodeStar/audiosilo-bridge#9 and KodeStar/audiosilo#80 (workspace glue, to follow).

User pages:

• New subsection in admin/podcasts.md: "Playing an episode that isn't downloaded".
• How retry and cooldown work, and the per-listener limit of 5 open fetches (admins exempt).

Developer pages:

• The 503 envelope and the fetch Status, the status and Retry routes, and the podcast_fetch capability.
• Fetch priorities and promotion, and the one-ahead queue prefetch.
• Claims: the reserved interactive worker, claim_min_priority negotiation, claim reissue, and lease release for an undelivered reply.
• A handoff for the player phase (2d) with the exact optional types, client and hook shapes, and polling rules. Nothing says the player shows any of this yet.

Removes the stale 404 not_downloaded claims. No UI changed, so no screenshots.

Every claim was checked against the code: server e4768eb, Bridge feat/bridge-2c-2b, and wire-2b.json. One review at high (/simplify and /code-review --fix). npm run build green.