[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/VulkanRenderer.h

@@ -659,7 +659,9 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         Bool m_baseTransformFlagsIsDefaultFbo = false;
         Bool m_baseTransformFlagsKeyValid = false;
         Uint32 m_baseTransformFlagsCache = 0;
-        Uint32 GetBaseTransformFlagsRaw();
+        // isDefaultFbo must be the default-ness of the CURRENTLY bound draw framebuffer;
+        // every caller already has it in hand from its own guards.
+        Uint32 GetBaseTransformFlagsRaw(Bool isDefaultFbo);
         // Drops every memoized pipeline handle. Required at command-buffer
         // boundaries and whenever any pipeline may have been destroyed. Also drops
         // the cached pipeline-state hash: the same boundaries can retire the GL