labeled block statements

TODO.md

@@ -391,9 +391,16 @@
     loop, a labeled one searches by label). The checker tracks a `loop_labels` stack and a
     `Yield_Target.defer_floor`; a `yield :L v` desugars to `slot = v; flush defers to L's body;
     break :L`, reusing the milestone-18 break lowering — **no new IR opcode, no emitter change**
-  - deferred (`// ponytail:`): a labeled bare block as a *plain statement* with `break :blk`;
-    `none`-before-concrete typing in an untyped block whose first concrete yield references a
-    block local (annotate instead)
+  - a labeled bare block as a *plain statement* is also exitable with `break :blk` (a HIR
+    `.Block` break target; not a loop, so unlabeled `break`/`continue` and `continue :blk` skip
+    it). The checker tracks a parallel `loop_is_loop` stack so labeled `break` reaches a loop or
+    block while `continue` and unlabeled `break`/`continue` reach only the innermost loop
+  - untyped block `none`-before-concrete typing now builds the block's leading (yield-free)
+    statements first (a throwaway probe), so a first concrete `yield :blk` that references a
+    block local still resolves the result to `?T`
+  - deferred (`// ponytail:`): the same `none`-before-concrete typing in an untyped block (or
+    loop) whose concrete yield references a local declared *past* the first yield (annotate);
+    same-label loop/block shadowing resolves innermost-wins
 
 21. unions and tagged unions