Pyramidize: show Original and Editor side by side on wide screens

[0xMMA]

Context

The Pyramidize view uses a tabbed layout for Original and Editor content (text-enhancement.component.ts:263-267). On wide monitors, the canvas area (flex: 1) stretches horizontally but the tabs still stack content vertically — wasting screen real estate.

Current Layout

┌──────────┬─────────────────────────────────────────┬───────────┐
│ Controls │  [Original] [Editor]  ← tabs             │ Trace Log │
│  280px   │  ┌──────────────────────────────────┐    │  260px    │
│          │  │ only one visible at a time        │    │           │
│          │  └──────────────────────────────────┘    │           │
└──────────┴─────────────────────────────────────────┴───────────┘

Expected (wide screens)

┌──────────┬──────────────────┬──────────────────┬───────────┐
│ Controls │ Original         │ Editor           │ Trace Log │
│  280px   │                  │                  │  260px    │
│          │                  │                  │           │
└──────────┴──────────────────┴──────────────────┴───────────┘

On wide viewports, Original and Editor should display side by side (no tabs). On narrower viewports, fall back to the current tabbed layout.

Relevant Code

• frontend/src/app/features/text-enhancement/text-enhancement.component.ts:263-267 — tab structure
• frontend/src/app/features/text-enhancement/text-enhancement.component.ts:676-686 — .canvas-area styles
• frontend/src/app/features/text-enhancement/text-enhancement.component.ts:699-746 — .tabs-container styles
• No max-width on the pyramidize page — it already fills available width

Acceptance Criteria

• Above a breakpoint, Original and Editor panels display side by side
• Below the breakpoint, falls back to current tabbed layout
• Both panels remain independently scrollable
• Trace log panel still works (collapsible) alongside the split view