A program with no 'main' reached the JIT entry-point call with a garbage
address (ORC reports lookup success but leaves main_addr degenerate), then
called it -> SIGSEGV. Add a pre-JIT entry-point check in main.zig that emits
'error: no main function found' and exits non-zero before codegen, plus a
defensive main_addr==0 guard in target.zig runJITFromObject as a backstop.
Regression: examples/1188-diagnostics-run-no-main.sx
- 0132: rewrite to the verified root cause -- protocol method signature
registration resolves type names via flat findByName and picks the wrong
same-name author. Original payload-field hypothesis kept as superseded;
repro switched to canonical `impl ... for` syntax. Still open (the
protocol path is unchanged).
- 0133: assigning a struct literal to a union member panics ("unresolved
type reached LLVM emission"); pre-existing, surfaced while testing.
- 0134: a same-name `error` set collapses into a namespaced import's set --
error-set declarations lack per-decl nominal identity (E6a gap); this is
what keeps the 0132-class error-ref resolution dormant.
