Hexagon linear-tile emission gate

src/emit/Kokoro.LinearTile.ps1 emits an FP32 row-major affine tile for the 3×768→512 ALBERT-to-BERT projection shape. PowerShell generates and validates the instruction stream; its scalar multiply-add loop is in the emitted V73 routine, not in the product PowerShell runspace. The tile takes a 12-byte geometry record, input, contiguous weight+bias buffer, and output, with length, pointer, and exact-dimension guards. It uses separate sfmpy and sfadd rounding, so numerical parity with the stock framework remains to be measured, not assumed.

tools/Test-HexagonEmission.ps1 -Kernel KokoroLinearTile -OutputDirectory build/hexagon-emission passed. The PowerShell-emitted ELF is 8,384 bytes; the routine is 504 bytes; its byte stream matched the independent pinned assembler exactly. Library SHA-256: EB507396900B71293E25B4B0C1B276D0EE574FF2E710088F54993A6EE117C37D. It has zero imports and relocations. The assembler digest is fc64c65aca06186106a73ba93e65ddf7c906bf4905b786dc748d3f034401ea27.

This is not a physical-device or numerical gate. The currently attached S23 has dev.mansfieldplumbing.kokorohexagon installed, but run-as reports that package is not debuggable. The historical AndroidSMA preview probe is not a substitute for exercising the independent Kokoro appliance. A verified private-artifact intake and dispatch path in that appliance is still needed before this tile can be compared on-device with the same input and weights.