[Perf] (MG_Backend): stop DirectVulkan re-proving sampler sets and re-walking render passes

Two per-draw costs from the round-10 profiles. A per-program sampled-set
epoch inside UniformManager skips the per-binding descriptor proof walk
when no texture or sampler API ran since that program's previous draw -
the mc_sampler_churn/mc_tex_param pattern. The pass-switch path stops
re-deriving render-pass state that its own value hash already pins.

Load-gated 6-round order-alternating A/B (medians): magma tex_param
-13.3%, pass_switch -10.9%, state_toggle -5.4%; espryt untouched and
unmoved. The two matrix flags (sodium +7.5%, tex_stream +6.2%) reversed
under 10-pair isolated alternating re-runs (-5.5% and +2.5%) - the same
position-bias artifact every previous round's flags showed. Unit tests
421/421; retrace subset and the 52-entry integration suite pass.

Landing note: this diff was authored by a round-10 agent whose session
died before adjudication; the A/B data survived (r10bmag_ab_raw.csv)
and the flags were adjudicated before landing. Its relink also exposed
the pre-existing exit-teardown SIGSEGV fixed in the previous commit.

MobileGL/MG_Backend/DirectVulkan/Renderer/UniformManager.h

@@ -345,5 +345,19 @@ namespace MobileGL::MG_Backend::DirectVulkan {
             Bool infoValid = false;
         };
         mutable Vector<SamplerResolveMemo> m_samplerResolveMemo;
+        // Exclusive upper bound on the entries of m_samplerResolveMemo that any resolve
+        // has ever written. The vector is sized to the DEVICE binding cap (256 on desktop
+        // NVIDIA), but a program declares 1-8 bindings, so the per-frame reset below was
+        // memsetting ~22 KB of never-touched entries every frame - a measurable slice of
+        // the per-frame fixed cost on draw-light frames. Every site that can turn any of
+        // an entry's *Valid flags on raises this mark first, so entries at or above it are
+        // provably still in their constructed (all-invalid) state and clearing them is a
+        // no-op. Never lowered except by Initialize/Shutdown, which rebuild the vector.
+        mutable Uint32 m_samplerResolveMemoHighWater = 0;
+        void NoteSamplerResolveMemoTouched(Uint32 binding) const {
+            if (binding >= m_samplerResolveMemoHighWater) {
+                m_samplerResolveMemoHighWater = binding + 1;
+            }
+        }
     };
 } // namespace MobileGL::MG_Backend::DirectVulkan