fix: resolve audit findings — stale text, dead code, build tags, docs

Assisted-by: MiMo V2.5 Pro

docs/ARCHITECTURE.md

@@ -97,10 +97,11 @@ fixed-arity instructions (`RET`, `NOP`, `JMP`, `CALL`) carry counts at all.
 
 Rules are conservative by design — silence beats a false positive.  The rules
 are `unknown-instruction`, `operand-count`, `undefined-label`,
-`duplicate-label`, `missing-ret`, `missing-textflag-include`, `abi-argsize` and
-`unreachable-code`.  Every diagnostic carries a stable code so callers can
-disable rules individually, and arch-specific rules switch off entirely when
-the target architecture cannot be inferred from the file name.
+`duplicate-label`, `missing-ret`, `missing-textflag-include`, `abi-argsize`,
+`unreachable-code`, `register-clobber`, `funcdata-pcdata`, `unused-label`,
+`invalid-textflag` and `stack-imbalance`.  Every diagnostic carries a stable
+code so callers can disable rules individually, and arch-specific rules switch
+off entirely when the target architecture cannot be inferred from the file name.
 
 Two things keep the rules honest on real-world code:
 
@@ -365,7 +366,7 @@ masked), reporting any encoding drift.
 
 ### `debug`
 
-The interactive debugger (Phase 4, linux/amd64).  It launches the target
+The interactive debugger (all four architectures).  It launches the target
 function in a child process that maps the JIT code, calls
 `PTRACE_TRACEME`, and stops; the parent attaches via ptrace and controls
 execution.  Breakpoints are patched as INT3 bytes through `/proc/pid/mem`