shader_recompiler/texture_pass: fall back to 8 when cbuf size is unknown

When ReadCbufSize returns 0 (unknown) we were defaulting to 1024 — the
ceiling — which silently overpays on every shader that takes the fallback
path. Use 8 instead, matching yuzu's original BINDLESS_ARRAY_LENGTH from
before the Tomodachi raise. If a shader genuinely needs more, that should
surface as a visible failure pointing back to its environment, not as
silent 1024-entry descriptor pools across the board.

src/shader_recompiler/environment.h

@@ -20,9 +20,9 @@ public:
 
     [[nodiscard]] virtual u32 ReadCbufValue(u32 cbuf_index, u32 cbuf_offset) = 0;
 
-    /// Returns the byte size of the const buffer at cbuf_index, or 0 if not bound.
-    /// Default returns 0 so that callers fall back to a conservative upper bound
-    /// when the environment can't provide a real size (e.g. disk-cache replay).
+    /// Returns the byte size of the const buffer at cbuf_index, or 0 if not bound /
+    /// not knowable from this environment. Callers treat 0 as "unknown" and fall
+    /// back to the original conservative default (e.g. disk-cache replay path).
     [[nodiscard]] virtual u32 ReadCbufSize([[maybe_unused]] u32 cbuf_index) {
         return 0;
     }

src/shader_recompiler/ir_opt/texture_pass.cpp

@@ -40,11 +40,12 @@ using TextureInstVector = boost::container::small_vector<TextureInst, 24>;
 constexpr u32 DESCRIPTOR_SIZE = 8;
 constexpr u32 DESCRIPTOR_SIZE_SHIFT = static_cast<u32>(std::countr_zero(DESCRIPTOR_SIZE));
 constexpr u32 BINDLESS_ARRAY_LENGTH = 1024;
+constexpr u32 BINDLESS_FALLBACK_LENGTH = 8;
 
 u32 BindlessCountForCbuf(Environment& env, u32 cbuf_index) {
     const u32 cbuf_size = env.ReadCbufSize(cbuf_index);
     if (cbuf_size == 0) {
-        return BINDLESS_ARRAY_LENGTH;
+        return BINDLESS_FALLBACK_LENGTH;
     }
     const u32 cbuf_descriptors = cbuf_size / DESCRIPTOR_SIZE;
     return std::min(std::max(cbuf_descriptors, 1u), BINDLESS_ARRAY_LENGTH);