quest: plan the follower gap that #5154's review found

quest/m0/broadcast-epoch/README.md

@@ -101,4 +101,5 @@ maintainer's pre-release merge of `release` into `main` keeps `main`'s
 - [Publish catalog restart](/quest/m0/broadcast-epoch/publish-catalog-restart.md) - `@moq/publish` never reuses catalog group numbers under one name and epoch after a re-announce
 - [Bindings](/quest/m0/broadcast-epoch/bindings.md) - moq-ffi and every wrapper expose the epoch and let a publisher announce one
 - [moqsrc](/quest/m0/broadcast-epoch/moqsrc.md) - moqsrc switches to the new broadcast on a `Restart`, keeping its pads by rendition name
+- [Follow gap](/quest/m0/broadcast-epoch/follow-gap.md) - a followed path reports a gap that ended its request, even onto a same-epoch covering prefix
 - [Stats totals and prefix tracks](/quest/m0/broadcast-epoch/stats-split.md) - the same release retires the per-path stats maps for totals and on-demand prefix tracks (decided 2026-10-05)

quest/m0/broadcast-epoch/follow-gap.md

@@ -0,0 +1,34 @@
+# [S] A followed path reports a gap that ended its request
+
+## Goal
+
+`origin::Consumer::follow` reports a gap that ended the request (an `End`
+then `Start`, or a `Restart`) even when the next serving route is a covering
+prefix with the same epoch, so `moq play` never misses a handoff while it is
+still draining the old run.
+
+## Plan
+
+Found by the OpenAI review of #5154 (2026-10-10), which added `follow` in
+moq-net and `@moq/net`. A same-epoch handoff from the exact route to a
+covering prefix, after a gap that ended the old request, reaches the Rust
+follower as an `Update`, because the announce cursor delivers by prefix and
+the follower never sees the gap. If that `Update` arrives while `moq play` is
+draining the old run, playback never restarts. JS sees the gap and is
+correct.
+
+Decided 2026-10-10: merge #5154 and fix the cause in moq-net here, in m0
+because the epoch line gates the release. Rejected: re-requesting in
+`moq play` whenever a run fails while the path is still served, which loops
+tightly on a broadcast that fails every time.
+
+Fix it in the announce cursor or the follower so the gap surfaces, matching
+JS. Regression with simulated time: an exact route ends, its request ends,
+then a same-epoch prefix route takes over while a reader is still draining;
+the follower must report the handoff, and `moq play` must restart. Leave the
+follower unpolled until the replacement is announced, since awaiting its
+`End` first avoids the bug and passes on the broken code, as
+`follow_keeps_a_gap_between_routes_of_one_epoch` does today.
+
+Public API: no new items, but `follow` reports a gap where it reported an
+`Update`, a behavior change to call out in the PR. Wire: none.