formats: teach the reference renderer the additive blend, and re-open 8 claims

The blend bit has been decoded against RB_BLENDCONTROL0 since 2026-08-31,
but ui_layout::blit could not draw it, and said so in a comment citing a
refutation that is <render-vs-capture> -- this renderer disagreeing with
itself while it had a stale keyframe association, no leaf geometry and no
rotation.

The consequence the port raised: verify-screen compares two renderers, so a
renderer that structurally cannot express a declared field makes the check
incapable on every screen that uses it -- 12 of 16 -- and the tolerance
silently excuses all of them. A quiet check is worse than a failing one.

Both equations come off the game's own pixel shader, which premultiplies
(oC0 = rgb*A, A), so only the blend register differs: 0x07010701 gives
rgb*A + dst*(1-A), 0x01010101 gives rgb*A + dst. Additive therefore
saturates rather than wrapping, and a transparent or black source is the
identity -- neither is a choice.

No plumbing needed: t8ad::parse already stores +0x04 as T8adImage::flags.

Four controls, pinned against arithmetic per the rotation precedent. The
fourth is the only one that can fail for the right reason: the first three
pass just as well if blit ignores the flag and draws everything additive,
so the discriminator flips only the blend on one sprite and requires two
different answers, each equal to its own equation. That is the same failure
class as the port's non-inverting latch check and my own backward scan that
resolved every guard to "internal".

120 passed, 0 failed on the full lib suite.

67 sprites over 14 screens were being drawn with the wrong blend, including
10 of 18 on the title and ptbtn00f, the PRESS (A) plate's highlight.

R1: tools/stale-instrument render-vs-capture lists 8 claims that died to
this instrument, including both legs of the rest() pair and "the plate-free
title capture may be too early to be settled", which sits on play-test
finding 3. None is re-derived here; this only records that the instrument
no longer exists in that form.

Also corroborates the port's H5: pgloading_loop5 is an ELEMENT resolving to
sprite pgloading_ring.t32, which is additive. I could not find loop5 as a
sprite in any pak and nearly reported a false contradiction from the
element/sprite name split.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Jc4pciRArGHfxGGhEbwp5t

docs/re/data/additive-elements-per-screen.txt

@@ -0,0 +1,100 @@
+# Which elements the reference renderer now draws ADDITIVE, per screen.
+# Source: T8aD +0x04 bit 0x02, docs/re/structures/ui-blend-mode-decoded.md.
+# Generated after ui_layout::blit gained an additive path (2026-09-01).
+# Before that change EVERY row below was drawn alpha-over by our renderer,
+# which is why `verify-screen` was structurally incapable on these screens.
+
+GP_TITLE entry 0  --  2 of 7 sprites additive
+    pgloading_circle1.t32
+    pgloading_delta.t32
+
+GP_TITLE entry 1  --  2 of 7 sprites additive
+    pgloading_circle1.t32
+    pgloading_delta.t32
+
+GP_TITLE entry 2  --  1 of 2 sprites additive
+    ptbtn00f.t32
+
+GP_TITLE entry 3  --  1 of 2 sprites additive
+    ptbtn00f.t32
+
+GP_TITLE entry 4  --  10 of 18 sprites additive
+    pteff01.t32
+    pteff03.t32
+    pteff03a.t32
+    ptlogo_back2eff1.t32
+    ptlogo_back2eff2.t32
+    ptlogo_back2eff3.t32
+    ptlogo_back2eff4.t32
+    ptlogo_back2eff5.t32
+    ptlogoall_eff.t32
+    ptlogoall_eff2.t32
+
+GP_TITLE entry 5  --  6 of 21 sprites additive
+    pteff03.t32
+    pteff03a.t32
+    pteff10.t32
+    pteff12.t32
+    ptframe1.t32
+    ptframe2.t32
+
+GP_TITLE entry 6  --  9 of 20 sprites additive
+    pteff03.t32
+    pteff03a.t32
+    pteff10.t32
+    pteff20.t32
+    pteff21.t32
+    pteff22.t32
+    pteff23.t32
+    ptframe3.t32
+    ptframe4.t32
+
+GP_TITLE entry 7  --  9 of 24 sprites additive
+    pteff03.t32
+    pteff03a.t32
+    ptlogo_back2eff1.t32
+    ptlogo_back2eff2.t32
+    ptlogo_back2eff3.t32
+    ptlogo_back2eff4.t32
+    ptlogo_back2eff5.t32
+    ptlogo_eff2.t32
+    ptlogo_eff3.t32
+
+GP_TITLE entry 8  --  6 of 21 sprites additive
+    pteff03.t32
+    pteff03a.t32
+    pteff10.t32
+    pteff12.t32
+    ptframe1.t32
+    ptframe2.t32
+
+GP_TITLE entry 9  --  9 of 20 sprites additive
+    pteff03.t32
+    pteff03a.t32
+    pteff10.t32
+    pteff20.t32
+    pteff21.t32
+    pteff22.t32
+    pteff23.t32
+    ptframe3.t32
+    ptframe4.t32
+
+GP_TITLE entry 12  --  3 of 9 sprites additive
+    pgloading_circle1.t32
+    pgloading_delta.t32
+    pgloading_ring.t32
+
+GP_TITLE entry 15  --  3 of 9 sprites additive
+    pgloading_circle1.t32
+    pgloading_delta.t32
+    pgloading_ring.t32
+
+GP_OPTIONS entry 19  --  3 of 16 sprites additive
+    po_menu_eff01.t32
+    po_menu_eff02.t32
+    po_menu_eff03.t32
+
+GP_OPTIONS entry 21  --  3 of 16 sprites additive
+    po_menu_eff01.t32
+    po_menu_eff02.t32
+    po_menu_eff03.t32