feat(ui): add collapsible left sidebar slicing, regex search, and breadcrumb bulk actions

[spelech]

Description

Introduces a Home Assistant-native 2-pane slicing interface, stacked multi-section filtering, instant regular expression & search syntax engine, and breadcrumb bulk actions to the Google Assistant Entity Console while preserving the user's active Home Assistant theme tokens.

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Visual Preview

1. Stacked Multi-Section Slicing (Not Exposed + Basement)	2. Search Syntax Specifiers (not:exposed basement)

3. Slicing Overview (Sidebar + Data Grid)	4. Regex Pattern Search (light\.(living|bar))

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Key Features

1. Stacked Multi-Section Sidebar Filtering:
   • Allows combining an Exposure State (Not Exposed, Exposed, etc.), an Area (Basement, Kitchen, etc.), and a Domain (Light, Switch, etc.) simultaneously.
   • Clicking an active filter item toggles it off.
   • Removable breadcrumb chips for each active facet ([Exposure: Not Exposed ✕] [Area: Basement ✕] [Domain: Light ✕]) plus a Clear All button.
2. Search Syntax & Specifier Engine:
   • Supports search command tokens parsed dynamically:
     • is:exposed, is:unexposed, not:exposed, is:override, has:alias
     • area:<name> or area:"Living Room"
     • domain:<domain>
     • floor:<floor>
   • Remaining query terms are evaluated as regex or case-insensitive substrings across friendly names, entity IDs, voice names, aliases, and areas.
3. Collapsible Sidebar Layout:
   • Sidebar toggles smoothly via ◀ / ▶ and top bar ☰; remembers collapsed state in localStorage.
   • Converts into an off-canvas drawer on mobile screens (< 768px).
4. Breadcrumb Bulk Actions:
   • One-click bulk action button (Expose All in Filter / Unexpose All in Filter) automatically scopes to the combined active filters.
5. Theme Preservation:
   • Strictly adheres to Home Assistant CSS tokens (--primary-background-color, --card-background-color, --secondary-background-color, --primary-text-color, --secondary-text-color, --primary-color, --divider-color).

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Verification

• Automated Tests: All 342 pytest integration tests passing (pytest tests/).
• Live Browser Verification: Tested live on Home Assistant with 764 entities; verified stacked multi-section filters, syntax queries, regex matching, and responsive sidebar.