[iterate-3M] Fix Xenos shader CF/fetch decode so the textured logo binds

The publisher splash (title idx0) rendered FLAT in ours while canary samples
a texture: ours never decoded the logo's textured pixel shader
(E59B2B3D, a `tfetch2D` sprite) even though our guest IM_LOADs the exact same
microcode canary does (verified byte-identical against the Wine oracle). The
shader was misparsed as flat. Three coupled bugs in the ucode decoder, all
off vs canary `gpu/ucode.h`:

1. CF opcode table was off-by-one (`control_flow.rs`): mapped opcode 0→Exec
   and 1→Exit, but Xenos has 0=kNop, 1=kExec, 2=kExecEnd, 3..6/13..14 the
   cond-exec variants, 7/8 loop, 9/10 call/return, 11 condjmp, 12 alloc,
   15 mark-vs-fetch-done. So a real `kExec` clause was read as a terminal
   `Exit`, truncating the CF block and dropping every instruction (incl. the
   `tfetch`) after it. Added Nop/MarkVsFetchDone variants; parse now ends on
   an END-bit exec clause.

2. exec/loop `address` is an absolute instruction-triple index from shader
   dword 0, but indexed our post-CF `instructions` slice directly
   (`ucode/mod.rs`). Rebase addresses by the CF triple count so `address*3`
   lands on the right instruction.

3. Fetch instruction bitfields were wrong (`ucode/fetch.rs`): `const_index`
   read from bit 5 (actually `src_reg`) instead of bit 20, and texture
   `dimension` from dword1 instead of dword2 bit14. The logo's `tfetch ..,tf0`
   was read as `tf1`, whose empty fetch-constant failed to decode → no
   texture. Also the `sequence` fetch/ALU bit is bit[0] of each pair, not
   bit[1] (`shader_metrics.rs`, `translator.rs`, `xenos_interp.wgsl`).

Result (--gpu-inline, deterministic 2x): the active PS's `tfetch_slots` now
resolves slot 0, the tf0 fetch-constant decodes (fmt K8888), and
`gpu.texture.decode` fires (137x at -n 50M; texture_cache_entries 0→1, the
only golden field that changed — all draw/swap counts unchanged). The same
fixes correct the WGSL uber-shader's fetch/CF walk for the threaded/--ui path.

Added a regression test that parses the real E59B2B3D microcode and asserts a
tfetch slot is found. Golden re-baselined (texture_cache_entries 0→1).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/xenia-app/tests/golden/sylpheed_n50m.json

@@ -6,5 +6,5 @@
   "swaps": 147,
   "unique_render_targets": 2,
   "shader_blobs_live": 6,
-  "texture_cache_entries": 0
+  "texture_cache_entries": 1
 }