feat(bluetooth): add native adapter-scoped management

[k8rito01]

Summary

• Use Bluetooth.defaultAdapter and its adapter-scoped device model for power, discovery, state, connect, disconnect, and forget.
• Remove fixed device truncation and keep the full list scrollable.
• Show pairing prompts, failures, and timeouts in the panel.
• Use bluetoothctl only as the interactive BlueZ PIN/passkey agent because Quickshell 0.3 does not expose a pairing-agent UI API.
• Offer Forget only for paired/saved devices.
• Document Quickshell 0.3+ and bluez-utils requirements.

Validation

• qmllint versions/V1/panels/BluetoothPanel.qml
• git diff --check
• Verified SplitParser receives non-newline interactive output chunks in an isolated Quickshell process.
• Scope: Bluetooth panel, Bluetooth icon mapping, and its compatibility note only.

[HANCORE-linux]

Thanks for splitting this out. Adapter-scoped devices, removal of the 12-device truncation, visible errors/timeouts, and keeping bluetoothctl only for interactive pairing are all good changes.

Two merge gates remain:

1. Quickshell rollout compatibility

The panel statically imports Quickshell.Bluetooth, while BluetoothPanel is eagerly instantiated by shell.qml. The installer currently checks only that qs exists; it does not enforce Quickshell 0.3. Updating an existing installation with an older Quickshell could therefore make the shell configuration fail to load. A README note alone does not protect Self-Update users.

Preferred fix:

• keep a small wrapper panel without the Bluetooth import;
• load the native Quickshell 0.3 implementation lazily;
• retain the current bluetoothctl implementation as the Loader-error/version fallback.

The alternative is a hard Quickshell 0.3 preflight in both installation and Self-Update before deployment, but that has a larger rollout blast radius.

2. Real pairing validation

The SplitParser test proves chunk delivery, but not that the selected BlueZ agent capability and stdin flow work with actual devices. Please provide or explicitly leave for maintainer runtime validation:

• connect/disconnect an already paired device;
• pair a normal new device;
• pair a device requiring PIN entry or passkey confirmation;
• reject/cancel pairing;
• pairing timeout;
• missing bluetoothctl should produce a direct dependency message instead of an ambiguous timeout/failure.

The native state/actions look structurally sound; these two points are what remain before merge.