Side quest 2: give three churning scenes something to develop

Curl Flow, Signal Decay and Circuit Bloom had no parameter that changed their
structure. Each was one process at one scale, statistically identical
everywhere and at every moment — which is the technical statement of "it
looks the same for five minutes". Every pixel moving, the image never
changing.

Each got the large-scale structure it was missing, and the slow axis now has
something real to walk:

- Curl Flow gains a CURRENT: one broad band carries the filaments and the
  rest runs bare. The axis is the band's strength rather than its position,
  and that choice was measured — moving the band preserves the frame's total
  energy, so a ten-second average of it is nearly the same image wherever it
  sits (0.0028 across a full sweep). Opening and closing it changes how much
  of the frame is lit at all. The current gates the final image rather than
  only the vein term, because the feedback trail and the flow tint each fill
  the frame on their own.
- Signal Decay gains a DAMAGE FRONT: lock falls away on one side of a moving
  boundary, so the stack has a shape instead of every lane being an
  independent coin flip. Hiss had to be gated by it too — hiss rises as lock
  falls, so without that a damaged lane simply traded signal for noise and
  carried the same energy, and the front cancelled itself out.
- Circuit Bloom now actually BLOOMS. `reach` was a fixed vignette, so the
  packets ran, the pads blinked and the board never changed. Its range stops
  at 1.6 because the frame's far corner is ~1.4 units out and travel spent
  past that changes nothing — the first attempt wasted most of the axis up
  there.

The gate itself was wrong, and this is the more important half of the commit.
It compared the scene at thirty seconds against the scene at two and a half
minutes and divided by what it did between those points with frozen
parameters. Those are two different places in the song, so the denominator
was full of audio reactivity: it was really asking "does the axis move this
scene MORE than the music does", which no scene should have to pass. Circuit
Bloom failed at 0.92x while its mean luminance moved 5.6x across the axis — a
large structural change scored as nothing.

The experiment now holds time constant and varies only the axis, against a
control that is the same parameters over the next window — the residual churn
the ten-second average failed to cancel, which is the noise floor it has to
beat. With the axis disabled the two parameter sets are identical and the
ratio is 0.00 by construction, so the companion check is a real discriminator
rather than a formality. It reads 0.00x on all six scenes.

Moiré Grid 28.7x · Gate Corridor 14.3x · Truchet Fold 3.3x · Signal Decay
1.9x · Curl Flow 1.7x · Circuit Bloom 1.4x, against a 1.25x bar.

104/104 checks pass including the slow set. Closes SIDE-QUESTS.md §2 and the
open half of EPIC-2.md §3.4.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

flow-state/EPIC-2.md

@@ -158,6 +158,15 @@ The middle row is the remaining work, and it is **not** mechanical: those scenes
 parameter that changes their structure, so they need shader changes that introduce one.
 Parameter automation cannot substitute for structure a scene does not have.
 
+**Closed by side quest 2** (SIDE-QUESTS.md §2). All three got the structure they were missing,
+and the measurement was corrected in the process — the ratios above were produced by an
+experiment that compared two different points in the SONG, so its denominator was full of audio
+reactivity and it was really asking "does the axis move this scene more than the music does".
+Circuit Bloom failed at 0.92× while its mean luminance moved 5.6× across the axis. The gate now
+holds time constant and varies only the axis, against the metric's own noise floor. Current
+figures: Moiré Grid 28.7× · Gate Corridor 14.3× · Truchet Fold 3.3× · Signal Decay 1.9× ·
+Curl Flow 1.7× · Circuit Bloom 1.4×, against a 1.25× bar, with the axis disabled reading 0.00×.
+
 ### 3.5 A framing layer
 
 The one that raises the ceiling rather than the floor. A shared zoom / crop / scale envelope