[fix2it]

Summary

This PR brings a comprehensive set of visual and engine enhancements to the Compact Fluent Quad theme and the windowing engine:

1. Dual-Account Mode (o / x) for Claude Code and OpenAI Codex: enables running two accounts concurrently side-by-side in the taskbar with ultra-compact markers.
2. Dual Antigravity Pools: displays both Gemini and Claude/GPT pools simultaneously with stacked 5-hour and 7-day gauges and distinct color grading.
3. Asymmetric 200ms Hover Crossfade: smooth on-demand inspection of weekly limits on hover, eliminating double-exposure ghosting.
4. Pace Tick Indicator: optional expected usage pace markers with a native context menu toggle.
5. Engine & Hit-Test Refactoring: consolidated animation ticking, single-lock O(1) hover hit testing, and safe Win32 timer lifecycle.

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Preview

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1. Multi-Account Support (o / x markers)

• Concept & Motivation: Addresses multi-account visibility requests discussed in [Theme Proposal] Headroom: Compact Widgets w/ Multiple Claude/Codex Account Support + Theme Picker Idea #157 (@Sekers) and custom config paths in Feature Request: support CLAUDE_CONFIG_DIR / custom credentials path for multi-account setups #75 (@juandanielreich).
• Design Innovation: Rather than multi-character badges that take up valuable taskbar width, we introduced ultra-compact single-character markers:
  • o: Primary account (default profile).
  • x: Secondary account (claude_x / codex_x profile, or any custom config_dir / credentials_path).
• Dynamic Sizing: Automatically expands the tile by +12 px only when dual mode is active; takes zero extra space when running a single account.
• Hover Crossfade: Hovering over a dual-account tile crossfades the session percentage/reset to the 7-day weekly reset for both accounts simultaneously.

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2. Antigravity Dual Pools & Visual Hierarchy

• Concurrent Rows:
  • Row 1: Gemini Models (dominant 6 px 5-hour bar + secondary 3 px 7-day bar underneath).
  • Row 2: Claude & GPT Models (dominant 6 px 5-hour bar + secondary 3 px 7-day bar underneath).
• Color Differentiation:
  • Gemini: Vibrant Teal (#5EEAD4 5h, #0D9488 7d).
  • Claude & GPT: Soft Sky / Steel Blue (#98D0E0 5h, #4A8B9E 7d).
  • Claude Terracotta: Restored standard #D97757 for 5h, with darkened #A44525 for 7d.
• Solo Mode: If only one pool is enabled, hovering smoothly crossfades between 5h and 7d without mid-transition brightness dips.

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3. Asymmetric Hover Crossfade (200 ms)

• Replaced linear crossfading with asymmetric_crossfade_opacities(progress):
  • Outgoing state fades out quickly ($0.0 \to 0.35$).
  • Incoming state fades in with early lead-in ($0.25 \to 1.0$).
  • Completely eliminates "double-exposure" text ghosting while preventing brightness dips at the midpoint.

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4. Pace Ticks

• Displays a subtle 1 px vertical tick on usage gauges showing the expected pacing for the current time window.
• Includes context menu toggle ("Show pace" / "Показывать темп") and accounts for late server resets.

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5. Architectural & DX Refactoring

• CrossfadeAnimation::tick_slot: abstracts frame throttling (15 ms), elapsed time interpolation, and slot completion across all providers.
• Safe Timer Lifecycles: AppState::is_any_crossfade_animating and stop_crossfade_timer_if_idle centralize Win32 WM_TIMER teardown, preventing timer starvation or premature cancellation.
• $O(1)$ Hit-Testing: tile_hover_at consolidates DPI scaling and surface checks into a single state acquisition per mouse move.
• Semantic Profile Queries: ProviderAccounts::is_profile_enabled and AppState::is_dual_mode_active.

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Verification & Test Suite

• Full Test Suite: All 612 unit and integration tests pass cleanly (cargo test).
• Formatting: Checked with cargo fmt --check.
• Live Verification: Verified on Windows 11 taskbar in both Dark and Light themes.