docs(morning): the 4-bar silence is the dN crossfade masking a silent eval

MORNING.md

@@ -106,3 +106,30 @@ turned out to be "the code did not compile".
 Full narrative is in the commit messages (they're written to be mined for the blog).
 
 **Nothing I touched needs a reload or a restart. `check-boot.sh` passes. Have fun. 🤘**
+
+---
+
+## ⚠️ Added after your first playthrough — read this one
+
+**The "drifts to silence over 4 bars" thing is not a drift.** `BootTidal.hs:100,126`:
+
+```haskell
+xfade i = transition tidal True (Sound.Tidal.Transition.xfadeIn 4) i
+d1 = xfade 1 . (|< orbit 0)
+```
+
+Every `dN` is a **4-cycle crossfade** — your "over 4 bars" is that exact number. So the
+sound you hear after ctrl+enter is the **previous** pattern fading out; the **new** one is
+already silent. The crossfade is working fine and has been *masking* a silent-eval bug by
+giving it a graceful exit.
+
+**The sound right after ctrl+enter is not evidence the eval worked** — it's evidence the
+last one did.
+
+Discriminator, 10 seconds: **eval the same track twice.** Silent from bar 1 the second
+time = confirmed. Then it's the usual silent-eval suspects — an unset `^NN` (which yields
+*no events*, not 0), or a block that didn't compile. `tools/check-tracks.sh` answers that
+for all 13 tracks at once and is runnable again.
+
+Tracked as **#79**, and it blocks #77 (silence-guard), #74 (the control AT — its 8s settle
+lands inside your fade) and #13 (transitions). Everything else can wait; this one can't.