Clean up daemon and improve readability

[luytan]

Description

Please include a summary of the changes and if applicable, a related issue.

If this PR introduce a new feature, explain your motivations

Fixes # (issue)

TODO

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Checklist:

• My code follows the style guidelines of this project (cargo fmt)
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the mdBook documentation
• My changes generate no new warnings (clippy/clang)
• New and existing unit tests pass locally with my changes (either use nix flake check or wait for the ci)

[Copilot]

Pull request overview

This PR refactors the cardwire daemon to improve readability by consolidating shared daemon state into a DaemonInner, splitting pre_daemon_tasks() into smaller helpers, and turning several background tasks into DaemonManager-provided futures. It also adjusts PCI/GPU monitoring and default-GPU selection to operate on the current GpuInterface map.

Changes:

• Refactor daemon state management (DaemonInner) and reorganize startup tasks into focused helper methods.
• Rework PCI udev monitoring to trigger GPU refresh via the in-process DebugInterface rather than a zbus proxy.
• Update default-GPU detection (check_default_drm_class) to operate on GpuInterface entries and apply it after refreshes.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
crates/cardwire-daemon/src/tasks/monitor_udev.rs	Switch PCI monitoring to use DebugInterface for refreshing GPUs.
crates/cardwire-daemon/src/models.rs	Introduce DaemonInner, refactor startup logic, and add task-future helpers.
crates/cardwire-daemon/src/interface/debug.rs	Adjust GPU refresh flow and default-GPU detection after rebuilding interfaces.
crates/cardwire-daemon/src/daemon.rs	Update main to spawn task futures from DaemonManager and align with refactor.
crates/cardwire-daemon/src/core/gpu/discover.rs	Change default-GPU detection to work with GpuInterface instead of GpuDevice.

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