feat(hslm): [H] φ-Scaled Dimensions — golden ratio architecture

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Parent: #329 — Fully Ternary Transformer

Level 0 (no dependencies) | ~60 LOC | New: src/hslm/phi_scaling.zig

Description

Scale model dimensions using the golden ratio φ = (1+√5)/2. Per-depth scaling φ^(-depth), FFN expansion φ× instead of 4×, residual scaling 1/√3, Xavier init for E[w²]=0.667.

Implementation

• layerScale(depth: u32) → f32 — φ^(-depth): {1.0, 0.618, 0.382, ...}
• ternaryInit(fan_in: u32) → []i2 — Xavier for ternary: E[w²] = 2/(fan_in+fan_out) ≈ 0.667
• ffnExpansion(model_dim: u32) → u32 — φ× expansion (round to nearest multiple of 3)
• residualScale() → f32 — 1/√3 ≈ 0.577

tri CLI

tri hslm phi-scale

Tests

• Trinity identity: φ² + 1/φ² = 3
• Layer scales decrease monotonically
• FFN dimensions divisible by 3
• Init variance ≈ 0.667

Blocks

• Issue L (Integration — model.zig uses φ scaling)

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Consolidated into feat(hslm) epic #329 — Fully Ternary Transformer