The hint's single-guard invariant was stated as "every path back to `starting` clears
the flag itself", enumerating Retry and a channel change. `onOptIn` is a third such
path and clears nothing, so the sentence was false as written — in the code comment,
in the Retry test's comment, and in docs/spa-conventions.md §5b.
Adding a clear to `onOptIn` would be dead code no test could distinguish, which is the
exact shape this branch removed from `onPlaying`. The omission is correct for a reason
none of the three places stated: the opt-in button renders only while `started` is
false, `started` only goes false in the render-phase reset that clears the flag two
lines later, and no player exists to set the flag while `started` is false. State that
exception, and pin the reachability premise it rests on with a test that fails if the
opt-in button outlives the mounted player.
Refs #554
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015QqCpYFsKgnAnx6jVwrKiV
timothyandClaude Fable 5.1
f119bfcb29