issues/0065: RESOLVED — value-block destructure parses

The block-value rework routes value-position `{ … }` through the same
statement parser as every other block, so a destructure decl (and any
statement form) inside a value-bound block now parses, with the trailing
expression as the block's value. The `defer { … }` half was fixed
earlier (634cf9b). Regression: examples/0042-basic-block-value-destructure.sx.

Gates: zig build test, run_examples.sh -> 344 passed.

examples/expected/0042-basic-block-value-destructure.exit

@@ -0,0 +1 @@
+12