Stop bodies blinking out, and give the cone a core and edges

The blinking was drawZombie validating its frame count against the LAST frame
only: a set with (say) z_h2 missing but z_h4 present kept N = 4, the walk cycle
stepped onto a name that had never loaded, and drawStatic silently drew nothing.
The body vanished for that frame of the cycle and came back on the next one,
forever. One cached 404 -- this project's oldest trap -- is enough to cause it.
It holds frame one now: a body that stops animating is a bug you can see, one
that flickers in and out reads as the game breaking. SPRV bumped to flush
whatever his phone has cached.

And no ctx.filter anywhere. The cut line was briefly the sprite redrawn clipped
to a band and flattened by a canvas filter, which put it exactly on the
silhouette -- and on the iPhone the line did not draw at all. Unsupported or
leaking past its restore, a rendering feature that fails silently on the target
device is not worth a pixel of polish. It is a plain bar again, brighter, and it
crosses the odd gap between the legs, which is the trade.

The cone gets the reference's look: a horizontal gradient across the width with a
near-white core down the centre line falling to blue at the edges, plus the depth
falloff along its length, plus stroked outer edges. Canvas has no 2D gradient, so
it is filled in eight slices each carrying its own across-gradient -- enough that
the seams vanish, which is what the old nested wedges got wrong.

Test mode: barrels gone (the rack already holds everything they would give you)
and the crowd raised to 16 bodies at a spawn every 0.9s, so it does not run dry
between kills.

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

config.js

@@ -234,11 +234,11 @@ export const TUNE = {
   // MEDIUM wave regardless of how far into a run you are, and every barrel weapon on the rack,
   // kept topped up so nothing runs dry mid-test. It overrides the difficulty director rather than
   // editing it — G.runGames keeps climbing underneath and the run is still a real run.
-  testZMax: 8,        // bodies on court: enough to test a crowd weapon, few enough to read
+  testZMax: 16,       // bodies on court. Was 8 and the sandbox kept running dry between kills — a
+                      // crowd weapon needs a crowd to test it against
   testZSpeed: 1.15,   // m/s shamble — medium, and FIXED (no per-game ramp)
-  testSpawnEvery: 1.6,// s between spawns
+  testSpawnEvery: 0.9,// s between spawns: they keep coming
   testLevel: 20,      // the roster level pickVariant pretends to be at, so every body type can turn up
-  testBarrelEvery: 14,// s between barrels, so the pickup itself is testable too
   // ---- THE LASER's wedge: aim and release like a serve, and a plane of light widens down the lane
   beamLen: 34,      // m it reaches. Was 26, which stopped at the far baseline and read as the beam
                     // being CUT OFF in mid-court; the player stands at z~24, so this carries it past