Brummel
e77060fdd4
plan: cycle 0002 node contract and ctx
Five tasks, each leaving the workspace green:
1. AnyColumn read-side as_f64/as_i64/as_bool/as_ts (mirror of as_*_mut).
2. Ctx<'a> + typed financial-indexed window accessors + tests.
3. Node trait + NodeSchema + InputSpec; lib.rs wiring + roadmap doc update.
4. Sma worked node in aura-std + hand-driven tests.
5. Workspace gate: build / test (20) / clippy -D warnings / purity grep.
Ordered so each compilation unit builds after its task (accessors → Ctx →
Node → Sma). Verbatim Rust + exact cargo commands per the planner Iron Law.