feat(asm): the operand forms and defines GOROOT writes

Assisted-by: GLM 5.3 Flash

CHANGELOG.md

@@ -7,6 +7,22 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [development]
 
+### Fixed
+
+- **The operand forms GOROOT writes.**  Numeric PC-relative jumps
+  (`JEQ 2(PC)`, the park loop `JMP 0(PC)`) resolve with the toolchain's
+  own instruction counting and fold jump-to-jump chains exactly as its
+  branch optimiser does; symbol immediates (`MOVQ $sym(SB), AX`)
+  assemble to the toolchain's RIP-relative LEA with an R_PCREL
+  relocation; negated constant expressions in operands (`ADJSP
+  $-(REGS - 8)`, the shape the cgo ABI macros write) fold; and `gasm
+  asm` predefines the `GOARCH_<arch>` and `GOOS_<goos>` macros the go
+  command passes to `go tool asm`, so GOROOT headers' `#ifdef
+  GOARCH_amd64` platform blocks (`go_tls.h`'s `get_tls` and friends)
+  select as intended.  The GOROOT corpus measure moves to 261 of 353
+  files assembling for every target architecture (73.9 %), 87.5 % of
+  the real-code corpus, from 70.8 % and 82.2 %.
+
 ### Added
 
 - **Per-architecture reference pages.**  [docs/asm/](docs/asm/README.md)