docs(shader): note that selected image-table records merge past the image and pair limits

docs/dev/ARCHITECTURE.md

@@ -136,7 +136,7 @@ flowchart LR
 
 A T# or S# that a shader loads from a buffer at a runtime offset (`key * stride + addend`, or `(key << n) & mask`) is not a direct descriptor. [`ResourceTracker.cpp`](../../core/shader/recompiler/Optimization/src/ResourceTracker.cpp) plans it as a table column (`TableColumn`): the heap V#'s descriptor source, the record stride and addend, the descriptor's offset in the record, and the key domains that may narrow it. Accesses with the same heap and record shape share one column. The shader keeps computing the offset and indexes a table binding: images use one variable-count `SAMPLED_IMAGE` array (`RuntimeAbi::ImageTableBinding`, in the fragment set when pipeline libraries split the sets), samplers a `SAMPLER` array (`Binding::SamplerTable`). Devices without `runtimeDescriptorArray`, `descriptorBindingPartiallyBound` and `descriptorBindingVariableDescriptorCount` refuse such shaders.
 
-A T# whose eight dwords and record offset the SRT walker can evaluate is planned as a selected column (`TableColumn::selected`): the offset is kept as a descriptor source (`TableColumn::selection`) and the shader indexes entry 0 of a one-record table. The column stays a whole table when the shader may write the memory its offset is read from at run time: the buffer it is read from, or any memory when the read or a write goes through a pointer or a GPU-only descriptor. Samplers are not selected: an S# the walker can evaluate is a direct sampler.
+A T# whose eight dwords and record offset the SRT walker can evaluate is planned as a selected column (`TableColumn::selected`): the offset is kept as a descriptor source (`TableColumn::selection`) and the shader indexes entry 0 of a one-record table. The column stays a whole table when the shader may write the memory its offset is read from at run time: the buffer it is read from, or any memory when the read or a write goes through a pointer or a GPU-only descriptor. Samplers are not selected: an S# the walker can evaluate is a direct sampler. When the selected columns would take a shader past `ShaderInfo::MaxImages` or `ShaderInfo::MaxSampledPairs`, `PlanTableColumns` plans the columns of one heap unselected again, the heap with the most selected columns first, until both fit.
 
 At every invocation, `TableSnapshotter` in [`ResourceMaterializer.cpp`](../../core/shader/recompiler/Optimization/src/ResourceMaterializer.cpp) reads each column's records from guest memory into `ResourceSnapshot::tables`: heap base and size, the record count (at most `ImageTableAbi::MaxKeys`), one code per record (an index into the distinct descriptor words, or a poison code) and the ranges it read. A selected column evaluates its offset and reads only that record, as the scalar loads would: dwords past the heap read zeros, an unmapped record or an offset that carries past 32 bits is poison, and an offset the walker cannot read faults the table instead of throwing. Its heap base moves to the record, so the shader's fault address and the written-heap check cover that record alone. Any other column narrows to the records its keys select, plus record 0, when every access has a key domain: a key buffer of at most 256 positions (`APS5_IMAGE_TABLE_KEY_SCAN`), or a value the SRT walker evaluates from user data, SRT reads and constants (which, for an image, selects its record before it could narrow). A loop-carried, lane-reduced or masked key keeps the whole column, so the cost of an invocation grows with the column's records and its distinct T#s. The snapshot is part of the invocation, not of the compiled variant: a changed table or key changes neither the SPIR-V nor the variant's disk key.