[vadde]

🎯 Summary

This PR delivers the Dynamic Adaptive Content Zoom & Stage Width Fit Engine for the DSA Living Documentation portal:

1. Screen-Width Bounded Zoom & Dynamic Fit Engine:
   • Dynamically calculates the available reading width and derives $Z_{\text{fit}} = W_{\text{avail}} / W_{\text{base}}$ ($100%$ on mobile, up to $175%$ on MacBook Pro, up to $200%$ on external 4K monitors).
   • Generates an adaptive ladder of 2 to 4 clean, punchy steps tailored to the active screen (e.g. 25% increments: $100% \to 125% \to 150% \to 175%$ on MacBook Pro; $100% \to 125% \to 150% \to 175% \to 200%$ on 4K display; 2 steps on compact laptops).
   • Dynamically adapts when moving between laptop displays and external monitors via debounced resize observers and sidebar toggle event synchronization.
2. Top Navigation Floating Bar Integration:
   • Liquid-glass segmented stepper pill in the top header controls cluster (#hud-zoom-stepper) featuring −, current % badge (click to reset to 100%), +, and one-click ⤢ Fit.
   • Scaled exclusively to .content-area / .stage-wrapper while the top HUD, navigation sidebar, and search/theater modals remain crisp and unaffected at 100% native scale.
3. Streamlined 38px Icon Squircle & Maximum Real Estate Recovery:
   • Stripped textual label (<span>Navigation</span>) from #floating-sidebar-toggle, converting it into an ultra-clean 38px × 38px cosmic glass squircle matching the top dock toggle.
   • Reduced collapsed left padding from 156px down to clamp(54px, 4vw, 72px), immediately reclaiming ~98px of horizontal width for the reading stage.
4. Mobile & Tablet Safeguards:
   • Automatically hides or locks zoom to 100% on viewports $\le 768\text{px}$, eliminating accidental horizontal scrolling and preserving responsive layout integrity.
5. Acoustic Haptics & Ergonomic Shortcuts:
   • Integrated with HapticAudio.tap() and HapticAudio.expand() on all zoom interactions.
   • Added keyboard shortcuts (Alt+= to zoom in, Alt+- to zoom out, Alt+0 to reset, Alt+F to fit).
   • State persisted in localStorage (dsa_content_zoom, dsa_content_fit).
6. Automated Gate 16 Headless Audit:
   • Implemented scripts/audit_dynamic_zoom_engine.py asserting stepper controls, CSS design tokens, clearance gutters, and multi-viewport dynamic step calculations.
   • Integrated into scripts/test-docs.sh (16-Gate Suite), Makefile (make test-zoom), and .github/workflows/ci.yml.