cli: Announce recovery secret switch

Entering a complete valid secret during interactive share recovery intentionally supersedes the partial share set. Previously that mode switch happened silently, which made correct behavior look like discarded input.

Emit one explicit notice only when shares were already accepted, and pin the behavior in the existing interactive recovery regression.

Refs #38

Author: codex

src/codex32/_cli_input.py

@@ -805,6 +805,8 @@ def allowed(candidate: CorrectionCandidate) -> bool:
         if one:
             return [artifact]
         if isinstance(artifact, Secret) and not basis:
+            if accepted:
+                _stderr("Complete secret supplied; using it instead of the accepted shares.")
             return [artifact]
         if not accepted:
             required = artifact.header.threshold

tests/test_cli.py

@@ -1155,6 +1155,7 @@ def answer(prompt: str) -> str:
     assert "Rejected:" not in captured.err
     assert "Share 1 of 3 accepted." in captured.err
     assert "Share 2 of 3 accepted." in captured.err
+    assert "Complete secret supplied; using it instead of the accepted shares." in captured.err
     first_prompt = (
         "Enter a codex32 string:\n> " if command[0] == "secret" else "Enter a codex32 string:\n> MS1"
     )