test-signals.sx: 17 tests covering signal basics (create, deref, reset!,
swap!), computed (derive, update, chain), effects (run, re-run, dispose,
cleanup), batch (deferred deduped notifications), and defisland (create,
call, children).
types.py: Island dataclass mirroring Component but for reactive boundaries.
evaluator.py: sf_defisland special form, Island in call dispatch.
run.py: Signal platform primitives (make-signal, tracking context, etc)
and native effect/computed/batch implementations that bridge Lambda
calls across the Python↔SX boundary.
signals.sx: Updated batch to deduplicate subscribers across signals.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>