docs(technical-debt): record DEPTH_BEFORE_SHADER in debt/libSceAgcDriver.md

docs/dev/debt/libSceAgcDriver.md

@@ -65,6 +65,7 @@
 - [Dual-source blending](../../../core/libs/prx/libSceAgcDriver/Graphics/src/State.cpp) (libSceAgcDriver) takes the MRT1 export as the second source of the MRT0 blend, as RADV and radeonsi program it; what the CB does with other export or target layouts is unknown, so they throw.
 - [DB_SHADER_CONTROL.CONSERVATIVE_Z_EXPORT](../../../core/libs/prx/libSceAgcDriver/Graphics/src/ShaderInputState.cpp) (libSceAgcDriver) becomes `DepthLess`/`DepthGreater`. For a pixel shader that breaks the promise, the host driver decides whether its interpolated Z is depth-tested before shading; what the console does then was not measured.
 - [DB_SHADER_CONTROL.STENCIL_TEST_VAL_EXPORT_ENABLE](../../../core/libs/prx/libSceAgcDriver/Graphics/src/State.cpp) (libSceAgcDriver) becomes `FragStencilRefEXT`, taken from the second MRTZ channel of the 32_GR and 32_ABGR formats as Mesa's AMD drivers write it ([`emit_ps_mrtz_export`](https://gitlab.freedesktop.org/mesa/mesa/-/blob/3e32b0e1f132231b7a972c1b0b5b06c7e16cf8b9/src/amd/common/nir/ac_nir_lower_ps_late.c#L194)); the console was not measured. The host value is the test value of both faces and what `REPLACE_TEST` writes, so a stencil operation that writes all ones or the operation value throws with it, as do a stencil clear draw, the UINT16_ABGR layout, `STENCIL_OP_VAL_EXPORT_ENABLE` and a device without `VK_EXT_shader_stencil_export` (NVIDIA's driver 610.57 offers none).
+- [DB_SHADER_CONTROL.DEPTH_BEFORE_SHADER](../../../core/libs/prx/libSceAgcDriver/Graphics/src/ShaderInputState.cpp) (libSceAgcDriver) becomes `EarlyFragmentTests`, and so does `Z_ORDER` `EARLY_Z_THEN_LATE_Z` or `EARLY_Z_THEN_RE_Z` without kill, Z export, mask export or stencil export; with alpha-to-coverage the tests stay late. The meaning of the bit and of `Z_ORDER` 3 follows Mesa (`src/amd/registers/gfx10.json`; RADV sets the bit for `early_fragment_tests` in `src/amd/vulkan/radv_shader.c`). What the console does with `DEPTH_BEFORE_SHADER` and a Z export, a mask export, a stencil export or alpha-to-coverage together was not measured.
 - [PA_SC_CONSERVATIVE_RASTERIZATION_CNTL](../../../core/libs/prx/libSceAgcDriver/Graphics/src/State.cpp) (libSceAgcDriver) - 0x6001 uses Vulkan overestimation on devices that add at most 1/256 pixel and keep degenerate triangles; the console's uncertainty region and degenerate handling are unmeasured. A value with `OVER_RAST_ENABLE` and `UNDER_RAST_ENABLE` clear is decoded as disabled even when `UNCERTAINTY_REGION_MODE` or the `OUTER_`/`INNER_UNCERTAINTY_EDGERULE_OVERRIDE` bits (19:16) are set, as PPSA01474 writes 0xe6000; that these fields have no effect without over- or underestimation is assumed from their names, not measured.
 - [Descriptor pool chain](../../../core/libs/prx/libSceAgcDriver/Graphics/src/ShaderResources.cpp) (libSceAgcDriver) - each pool holds two storage buffer descriptors more than a set can take, as a workaround: RADV (Mesa 26.0 and later) lets a `FREE_DESCRIPTOR_SET` pool place a set up to 32 bytes past the pool's buffer ([`util_vma_heap_init`](https://gitlab.freedesktop.org/mesa/mesa/-/blob/main/src/amd/vulkan/radv_descriptor_pool.c) is given `bo_size + RADV_POOL_HEAP_OFFSET` as a size), and with a page-multiple pool size those bytes are an unmapped page
 - [CMASK fast clears](../../../core/libs/prx/libSceAgcDriver/Graphics/src/Draw.cpp) (libSceAgcDriver) - each fast-cleared CMASK tile (code 0) is stored as `CB_COLOR_CLEAR_WORD` into its 8x8 texels at the first draw into the target or at its fast-clear eliminate or DCC decompress pass, not as the color block writes the tile, and the CMASK is then stored as expanded (0xF): a texture or copy read of the target after that draw and before the title's eliminate sees the clear value in tiles no draw wrote, where the console keeps their previous bytes. Tile addresses follow the pipe-aligned SW_64KB_Z_X CMASK equation for 16 pipes; other CMASK swizzle modes, a cleared tile of a DCC target and a fast clear of a mipmapped, 3D or array color target throw. A tile with a code other than 0 and 0xF keeps its texels like an expanded tile: PPSA18391 (engine: Clickteam Fusion) fast clears a target whose CMASK it never initialized, so some of its nibbles hold leftover values such as 1 and 10; what the console does with such codes on a single-sample target is unverified on hardware