feat(parser): macro expansion, conditionals and include splicing with -I

Assisted-by: GLM 5.3 Flash

docs/man/gasm-audit-instructions.1

@@ -2,7 +2,7 @@
 .SH NAME
 gasm-audit-instructions \- diff the encoder against the Go toolchain, or measure a corpus
 .SH SYNOPSIS
-.B gasm audit\-instructions [\-\-corpus [\fIdir\fR]] [amd64|arm64|riscv64|loong64]
+.B gasm audit\-instructions [\-\-corpus [\fIdir\fR]] [\-I dir] [amd64|arm64|riscv64|loong64]
 .SH DESCRIPTION
 Compare the gasm encoder for the given architecture (default amd64)
 against
@@ -38,6 +38,12 @@ second.
 .B \-\-corpus [\fIdir\fR]
 Assemble a corpus of .s files and report pass rates and failure
 reasons.
+.TP
+.B \-I \fIdir\fR
+Directory to search for #include files; may be repeated, searched in
+order after the source directory.  A corpus run whose files include
+toolchain headers (such as GOROOT/pkg/include) needs it, the same -I a
+toolchain comparison takes.
 .SH EXIT STATUS
 The mnemonic-diff mode reports through its output and exits 0; a failed
 probe or an unknown architecture exits non-zero.