docs: Sonix as built, and the island line in AGENTS.md

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/docs/superpowers/specs/2026-11-07-sonix-player-design.md b/docs/superpowers/specs/2026-11-07-sonix-player-design.md
index 5ab7794..44a20c7 100644
--- a/docs/superpowers/specs/2026-11-07-sonix-player-design.md
+++ b/docs/superpowers/specs/2026-11-07-sonix-player-design.md
@@ -192,3 +192,20 @@ No draft and no dirty mark: the page edits no file.
 - API calls are checked against a live player. The canvas, the panel and the
   page are checked by eye, by the user; the agent confirms loading from the
   `qs` log.
+
+## As built
+
+Differences from the design above, found while building it:
+
+- The boot logo page is in its own sidebar group, HiBy R1, not Appearance.
+- The panel's cover comes from `/api/art?path=<track>&max=256`, which can
+  answer 202 while it prepares; the panel retries three times per track.
+- The heart sends `favourite` with the path and 1 or 0.
+- SonixLink's `bitrate` is in bits per second; the panel shows kbps.
+- Folders browses from an empty path: the player answers `path=/` with
+  plain text, "outside the card". A folder plays as its first file with the
+  folder as the list, since `play_all` refuses a folder.
+- The beacon helper is restarted after a fixed 5s, not a growing backoff.
+- New playlist adds a draft row with a hint; it does not switch tabs.
+- An open island panel closes when the player leaves, rather than showing
+  a message; the drawer page shows the message.