tests

Goal

Comprehensive labeled_blocks.ori tests with parity, negative continue:block pin, and loop-transparency coverage.

Author tests/spec/expressions/labeled_blocks.ori from the proposal examples; verify interpreter==LLVM; add #compile_fail pins.

labeled-block-early-exit-proposal.md (all examples); tests.md Matrix + Interaction + Negative Testing.

tests/spec/expressions/labeled_blocks.ori: basic block:done { break:done v }, break-with-value type unification, nested blocks (independent exit), block-inside-loop with bare-break-targets-loop, break:outer/continue:outer transparency through a block, lexer-classifier + validator examples.
Negative pins: #compile_fail for continue:block_label (blocks do not iterate); block used as bare identifier compiles fine (positive). Dual-execution parity for every positive test (interpreter == LLVM).