iter ct.1.4-followup: type-con rewrite test + doc clarity

crates/ail/src/main.rs

@@ -228,10 +228,21 @@ enum Cmd {
     /// ct.1 (dev-only): rewrite every `*.ail.json` under `<dir>` so
     /// that bare cross-module `Type::Con` and `Term::Ctor.type_name`
     /// references gain their owning module's qualifier. Idempotent.
-    /// Uses the first-match-in-imports-order disambiguation rule
-    /// (matches iter 23.1.3's imports-fallback) so the rewrite never
-    /// silently changes which type a fixture resolves to. Prelude is
-    /// treated as an implicit last-resort fallback.
+    ///
+    /// Disambiguation: the first import (in declaration order) that
+    /// owns a matching type wins. Ties are NOT diagnosed — the
+    /// migration silently picks the first match. Prelude is consulted
+    /// as an implicit last-resort fallback when no listed import owns
+    /// the name.
+    ///
+    /// Note: this is one-shot dev tooling and intentionally weaker
+    /// than the typecheck-time `ambiguous-type` diagnostic shipped in
+    /// iter 23.1.3, which fires through the type-checker on multi-
+    /// import collisions. The two are different rules at different
+    /// layers; do not assume parity. The expected usage is to run
+    /// the migration once on a fixture corpus that does not exhibit
+    /// genuine multi-import ambiguity, then let the typechecker
+    /// enforce the stricter rule going forward.
     MigrateCanonicalTypes {
         /// Directory containing `*.ail.json` to migrate (typically
         /// `examples/`).