docs: changelog and readme for the instruction wave and the honest corpus rate

Assisted-by: GLM 5.3 Flash

CHANGELOG.md

@@ -9,6 +9,29 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+- **The GOROOT instruction wave, part 1.**  The encoder now covers the
+  instruction families GOROOT's real code uses that gasm lacked,
+  byte-verified against `go tool asm`: on amd64 the carry ALU, the
+  atomics (CMPXCHG, XADD, XCHG), AES-NI, SHA-1/256, PCLMULQDQ, CRC32,
+  GFNI, ADX, BMI, the string primitives, the system set (CPUID, RDTSC,
+  SYSCALL, fences, MXCSR) and the SSE/AVX/EVEX gaps; on arm64 the pair
+  loads and stores (LDP/STP), acquire/release and LSE atomics, AES and
+  SHA, the system operations, the bit ops and the NEON slice including
+  structure loads and the literal-pool moves; on riscv64 the RV64A AMO
+  family with aq/rl ordering, the Zbb pseudos with their RVC
+  compressions, the FMA forms and the RVV slice with `vsetvli`/
+  `vsetivli`; on loong64 the AM atomics with acquire/release forms, the
+  LSX/LASX slice, the `VMOVQ`/`XVMOVQ` transfer family and FSEL.
+  Also fixed on the way: arm64 `CASD`/`CASW` lacked an opcode bit, and
+  riscv64 `VSETVLI` with an immediate length now canonicalises to
+  `vsetivli` as the toolchain does.
+- **The corpus audit measures honestly.**  Files named for Go ports gasm
+  does not target (arm, 386, s390x, ...) are no longer attempted for the
+  four supported architectures (no supported build compiles them), and
+  the headline rate is reported over attemptable files: 136 of 433 on
+  the full corpus (31.4 %), 135 of 383 on real code (35.2 %), from the
+  127 that the previous release measured.  The probe battery that
+  decides encodability gained the operand shapes the new families use.
 -
 
 ## [0.34.0] - 2026-09-20