feat(web): implement complete workspace with themes, tabs, sidebar, and mobile

Transform CalcText from a single-document calculator into a full workspace
application with multi-document support, theming, and responsive mobile experience.

- Theme system: 5 presets (Light, Dark, Matrix, Midnight, Warm) + accent colors
- Document model with localStorage persistence and auto-save
- Tab bar with keyboard shortcuts (Ctrl+N/W/Tab/1-9), rename, close
- Sidebar with search, recent, favorites, folders, templates, drag-and-drop
- 5 templates: Budget, Invoice, Unit Converter, Trip Planner, Loan Calculator
- Status bar with cursor position, engine status, dedication to Igor Cassel
- Results panel: type-specific colors, click-to-copy, error hints
- Format toolbar: H, B, I, //, color labels with live preview toggle
- Syntax highlighting using theme CSS variables
- Error hover tooltips
- Mobile: bottom results tray, sidebar drawer, touch targets, safe areas
- Docker multi-stage build (Rust WASM + Vite + Nginx)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

_bmad-output/_progress/wds-project-outline.yaml

@@ -0,0 +1,50 @@
+# WDS Project Outline
+# Generated: 2026-03-17
+# Phase 0: Project Setup
+
+project_name: CalcText
+project_type: brownfield
+product_complexity: complex
+tech_stack: react
+component_library: custom
+root_folder: "_bmad-output"
+brief_level: simplified
+design_system_mode: recommended
+
+existing_materials:
+  has_materials: false
+  notes: "Brainstorm insights from party mode session available in conversation context"
+
+project_context:
+  stakes: enterprise
+  description: "Cross-platform notepad calculator evolving into a full workspace application"
+
+working_relationship:
+  involvement: autonomous
+  user_role: project_manager
+  recommendation_style: direct_guidance
+  stakeholder_notes: null
+
+# Brownfield Context
+brownfield:
+  existing_product: "CalcText Web App"
+  tech_stack_detail: "React 19 + CodeMirror 6 + Vite 7 + WASM engine"
+  current_state: "Two-column editor (input + results), PWA, light/dark theme"
+  evolution_goals:
+    - "Multi-theme system (Light, Dark, Matrix, custom)"
+    - "Tab system for multiple calctext documents"
+    - "File sidebar with folders and organization"
+    - "User accounts and cloud persistence (deferred - backend)"
+    - "Elevated results panel design"
+    - "Mobile experience redesign"
+
+# Phase Routing
+phases:
+  phase_0: completed
+  phase_1: "simplified brief (brownfield)"
+  phase_2: skipped
+  phase_3: "scenarios from brownfield analysis"
+  phase_4: "UX design with Freya"
+  phase_5: "custom component development"
+  phase_7: "design system extraction"
+  phase_8: "product evolution entry point"