feat: add interactive workspace overview

[qeude]

Summary

• Add an interactive overview of workspaces and window columns.
• Support workspace navigation, window focusing, dragging, stacking, and floating-window placement.
• Add configurable overview zoom and optional window previews.
• Add the toggle-overview command and default <mod>-o hotkey.
• Add overview projection, runtime, macOS controller, preview, and coverage tests.

Testing

• Not run: swift build
• Not run: swift test
• Not run: ./script/build_and_run.sh --verify
• Not run: desktop smoke tests via ./script/test_desktop.sh

[greptile-apps]

Greptile Summary

The PR adds an interactive workspace overview with keyboard and pointer navigation, window movement, optional previews, and configuration support.

• Adds pure overview projection, hit-testing, drop targeting, and runtime state transitions.
• Adds macOS panels, navigation, dragging, preview capture, and preview-cache lifecycle management.
• Integrates overview commands, hotkeys, daemon synchronization, border suppression, configuration, documentation, and tests.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains.

Important Files Changed

Filename	Overview
Sources/DefiMacOS/OverviewPreviewCapture.swift	Captures optional previews through ScreenCaptureKit and now validates the captured window owner before accepting pixels.
Sources/DefiMacOS/OverviewController.swift	Implements overview panels, selection, navigation, dragging, viewport animation, and guarded preview caching.
Sources/DefiRuntime/OverviewRuntime.swift	Adds validated pure-runtime transitions for overview focus, workspace selection, and window drops.
Sources/DefiDaemon/DaemonOverview.swift	Wires overview interactions into runtime transitions, native layout application, focus, persistence, and snapshot refresh.
Sources/DefiCore/Overview.swift	Adds pure overview projection, hit-testing, viewport interpolation, and drop-target calculation.

Sequence Diagram

sequenceDiagram
    participant User
    participant Controller as OverviewController
    participant Daemon
    participant Runtime as DefiRuntime
    participant Platform as macOS Platform

    User->>Controller: Navigate, select, or drag
    Controller->>Daemon: Focus/workspace/drop intent
    Daemon->>Runtime: Validate and reduce state
    Runtime-->>Daemon: Updated monitor/workspace result
    Daemon->>Platform: Apply layout and focus
    Daemon->>Controller: Refresh overview snapshot
    Controller-->>User: Render updated overview

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_{Reviews (3): Last reviewed commit: "Merge branch 'main' into feat/niri-overv..." | Re-trigger Greptile}