Adds reactive variants of the `Sequence` and `Select` behavior nodes.
(originally requested here https://github.com/Sollimann/bonsai/issues/70
)

By default, a `Sequence`/`Select` keeps memory across ticks and it
resumes whichever child was running. The new memoryless variants re-walk
children from the first one on every tick, so earlier conditions are
re-checked and a running child can be aborted or preempted.

Key changes:

1. New `.memory(false)` builder on `Sequence`/`Select` to opt into
reactive behavior (e.g. `Sequence(...).memory(false)`).
2. Visualizer support, so that memoryless nodes render with a dashed
circle; telemetry/serde round-trip handled.
3. `memoryless_chase` example (chase-while-visible + priority preemption
demos) and updated `visualizer_smoke`.
4. Tests: behavior, allocation, telemetry, and serde round-trip
coverage.
5. Housekeeping: Bump version number, update python bindings, update
docs and README