P5: track index.d.ts + reject invalid periods in the Node binding (#83)

* build(node): track the generated index.d.ts (P5.1)

index.js was committed but index.d.ts was gitignored, an inconsistency that
also contradicts CONTRIBUTING ('regenerate both .d.ts/.js when a binding API
changes'). Track index.d.ts too so the repo carries the TypeScript types as a
matched pair with index.js. Generated by napi build; ~214 indicator classes.

* fix(node): reject invalid periods instead of clamping them (P5.4)

The Node scalar-indicator macro clamped period 0 to 1 (via clamp_period + must)
and the multi-parameter constructors did the same, silently swallowing the
core's PeriodZero validation. The core rejects period 0 (Error::PeriodZero),
and the Python and WASM bindings already propagate it — Node was the outlier,
masking caller mistakes. Make the macro constructor fallible and let every
constructor propagate the core error via map_err, removing clamp_period/must.
Update the smoke test (period 0 now throws, matching core/Python/WASM).

* docs(changelog): note the Node period-validation change (P5.4)

Behavior change per CONTRIBUTING: Node constructors now reject invalid periods
instead of clamping. Add an [Unreleased] Changed entry.

* chore: drop accidentally committed scratch log

CHANGELOG.md

@@ -7,6 +7,13 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+- **Node binding: invalid indicator periods now throw instead of being silently
+  clamped.** The scalar-indicator constructors previously clamped `period = 0`
+  to `1`; every Node constructor now propagates the core's validation error
+  (e.g. `period must be greater than zero`), matching the Python and WASM
+  bindings and the Rust core. Constructing with a valid period is unaffected.
+
 ## [0.3.1] - 2026-05-30
 
 ### Fixed