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>

_scripts/smoke-test.sh

@@ -0,0 +1,95 @@
+#!/usr/bin/env bash
+# smoke-test.sh — Quick verification of CalcPad CLI and web app
+set -euo pipefail
+
+PASS=0
+FAIL=0
+SKIP=0
+
+pass() { echo "  PASS: $1"; ((PASS++)); }
+fail() { echo "  FAIL: $1"; ((FAIL++)); }
+skip() { echo "  SKIP: $1"; ((SKIP++)); }
+
+# ─── CLI Tests ──────────────────────────────────────────────────────────────────
+
+echo ""
+echo "=== CLI Tests ==="
+
+if command -v cargo &>/dev/null; then
+
+  # 1. Basic arithmetic
+  result=$(cargo run -q -p calcpad-cli -- "2 + 3" 2>/dev/null)
+  if [[ "$result" == *"5"* ]]; then pass "arithmetic: 2 + 3 = 5"
+  else fail "arithmetic: expected 5, got '$result'"; fi
+
+  # 2. Pipe / stdin
+  result=$(echo -e "x = 10\nx * 3" | cargo run -q -p calcpad-cli 2>/dev/null)
+  if [[ "$result" == *"30"* ]]; then pass "pipe/stdin: x=10, x*3 = 30"
+  else fail "pipe/stdin: expected 30 in output, got '$result'"; fi
+
+  # 3. JSON output
+  result=$(cargo run -q -p calcpad-cli -- --format json "42" 2>/dev/null)
+  if [[ "$result" == *"42"* ]] && [[ "$result" == *"{"* ]]; then pass "JSON output"
+  else fail "JSON output: expected JSON with 42, got '$result'"; fi
+
+  # 4. Error exit code for invalid input
+  if cargo run -q -p calcpad-cli -- "???invalid???" &>/dev/null; then
+    fail "error exit code: expected non-zero exit"
+  else
+    pass "error exit code: non-zero on bad input"
+  fi
+
+  # 5. cargo test suite
+  if cargo test --workspace -q 2>/dev/null; then pass "cargo test --workspace"
+  else fail "cargo test --workspace"; fi
+
+else
+  skip "CLI tests (cargo not found)"
+fi
+
+# ─── Web Tests ──────────────────────────────────────────────────────────────────
+
+echo ""
+echo "=== Web Tests ==="
+
+WEB_URL="${WEB_URL:-http://localhost:8080}"
+
+if curl -sf "$WEB_URL" &>/dev/null; then
+
+  # 1. index.html returns 200
+  status=$(curl -sf -o /dev/null -w "%{http_code}" "$WEB_URL/")
+  if [[ "$status" == "200" ]]; then pass "index.html 200"
+  else fail "index.html: got HTTP $status"; fi
+
+  # 2. HTML contains expected content
+  body=$(curl -sf "$WEB_URL/")
+  if [[ "$body" == *"CalcPad"* ]]; then pass "HTML contains CalcPad"
+  else fail "HTML missing CalcPad title"; fi
+
+  # 3. WASM JS glue is served
+  wasm_js_status=$(curl -sf -o /dev/null -w "%{http_code}" "$WEB_URL/wasm/calcpad_wasm.js")
+  if [[ "$wasm_js_status" == "200" ]]; then pass "WASM JS served"
+  else fail "WASM JS: got HTTP $wasm_js_status"; fi
+
+  # 4. WASM binary content-type
+  ct=$(curl -sf -o /dev/null -w "%{content_type}" "$WEB_URL/wasm/calcpad_wasm_bg.wasm")
+  if [[ "$ct" == *"wasm"* ]]; then pass "WASM content-type: $ct"
+  else fail "WASM content-type: expected wasm, got '$ct'"; fi
+
+  # 5. SPA fallback — non-existent route returns index.html
+  fallback=$(curl -sf "$WEB_URL/nonexistent/route")
+  if [[ "$fallback" == *"CalcPad"* ]]; then pass "SPA fallback"
+  else fail "SPA fallback: did not return index.html"; fi
+
+else
+  skip "Web tests ($WEB_URL not reachable — run 'docker compose up -d' first)"
+fi
+
+# ─── Summary ────────────────────────────────────────────────────────────────────
+
+echo ""
+echo "=== Summary ==="
+echo "  Passed: $PASS  Failed: $FAIL  Skipped: $SKIP"
+
+if [[ $FAIL -gt 0 ]]; then exit 1; fi
+exit 0