feat(indicators): A5b Fibonacci tools (geometric) (#172)

Completes the **Fibonacci** family with the four geometric/time tools (catalogue 373 -> 377). All extend the internal `pattern_swing` ZigZag tracker with a per-pivot bar index and a current-bar counter (additive — the chart/harmonic detectors are unaffected), and emit `Candle -> struct` outputs via custom Python/Node/WASM bindings.

| Tool | Output |
|------|--------|
| `FibFan` | three trendlines fanning from a swing start through its 38.2/50/61.8% retracement levels, extended to the current bar |
| `FibArcs` | semicircular retracement levels centred on the swing end, normalised by the leg's bar-width (chart-scale-free) |
| `FibChannel` | a sloped base trendline plus parallel lines at Fibonacci multiples of the channel width |
| `FibTimeZones` | markers at Fibonacci bar-distances (1/2/3/5/8/...) from the latest swing pivot |

The geometric tools are novel as streaming indicators; each normalises its geometry to the swing leg's bar-width so the output is chart-scale-free. Formulas are documented in each module and deep-dive.

Fully wired: core (100% unit-tested branches incl. the new `pattern_swing` bar tracking), Python/Node/WASM struct bindings, fuzz, reference + streaming-vs-batch tests.

Verification: `cargo test --workspace` green, clippy `-D warnings` clean, node 454 tests, python 768 tests.

bindings/node/index.d.ts

@@ -402,6 +402,26 @@ export interface FibConfluenceValue {
   price: number
   strength: number
 }
+export interface FibFanValue {
+  fan382: number
+  fan500: number
+  fan618: number
+}
+export interface FibArcsValue {
+  arc382: number
+  arc500: number
+  arc618: number
+}
+export interface FibChannelValue {
+  base: number
+  level618: number
+  level1000: number
+  level1618: number
+}
+export interface FibTimeZonesValue {
+  onZone: number
+  barsToNext: number
+}
 export type SmaNode = SMA
 export declare class SMA {
   constructor(period: number)
@@ -3926,3 +3946,39 @@ export declare class FibConfluence {
   isReady(): boolean
   warmupPeriod(): number
 }
+export type FibFanNode = FibFan
+export declare class FibFan {
+  constructor()
+  update(high: number, low: number): FibFanValue | null
+  batch(high: Array<number>, low: Array<number>): Array<number>
+  reset(): void
+  isReady(): boolean
+  warmupPeriod(): number
+}
+export type FibArcsNode = FibArcs
+export declare class FibArcs {
+  constructor()
+  update(high: number, low: number): FibArcsValue | null
+  batch(high: Array<number>, low: Array<number>): Array<number>
+  reset(): void
+  isReady(): boolean
+  warmupPeriod(): number
+}
+export type FibChannelNode = FibChannel
+export declare class FibChannel {
+  constructor()
+  update(high: number, low: number): FibChannelValue | null
+  batch(high: Array<number>, low: Array<number>): Array<number>
+  reset(): void
+  isReady(): boolean
+  warmupPeriod(): number
+}
+export type FibTimeZonesNode = FibTimeZones
+export declare class FibTimeZones {
+  constructor()
+  update(high: number, low: number): FibTimeZonesValue | null
+  batch(high: Array<number>, low: Array<number>): Array<number>
+  reset(): void
+  isReady(): boolean
+  warmupPeriod(): number
+}