Update README development status and add a Whale IR example #887

Motivation

README.md still says active pre-beta development while Cargo uses 0.0.1-alpha-dev. The documented first program uses printing and native run, which the opt-in Whale adapter does not support.

Scope

Update the development status and add a short scalar --whale check/build --emit=ir example. State Linux amd64/O0/IR-only limits and LLVM default. Keep the normal LLVM quick start. Use README/examples; no language specification or new process documentation.

Difficulty: easy.

Completion criteria

• Commands produce verified .wir with a compiler from the checkout.
• Avoid claims of native Whale execution or parity.
• Keep supported LLVM/release targets accurately described.