chore: commit durable overlay state (configs, patches, recipe symlinks)

Pre-existing work from other sessions committed as durable state:
- local/config/drivers.d/ (8 driver configs)
- local/config/firmware-fallbacks.d/ (3 firmware configs)
- local/patches/base/, kernel/, relibc/ (new patch carriers)
- recipes/system/ symlinks (driver-params, acmd, ecmd, usbaudiod)

pkgar build artifacts and cache intentionally excluded.

local/config/firmware-fallbacks.d/00-amdgpu.toml

@@ -0,0 +1,14 @@
+# AMD GPU firmware fallback chains
+# If a specific DMCUB firmware is not found, try earlier versions
+
+[[fallback]]
+pattern = "amdgpu/dmcub_dcn31.bin"
+chain = ["amdgpu/dmcub_dcn30.bin", "amdgpu/dmcub_dcn20.bin"]
+
+[[fallback]]
+pattern = "amdgpu/dmcub_dcn30.bin"
+chain = ["amdgpu/dmcub_dcn20.bin"]
+
+[[fallback]]
+pattern = "amdgpu/gc_11_0_0_mes_2.bin"
+chain = ["amdgpu/gc_10_3_0_mes_2.bin"]