feat: add bec signal info

[wakonig]

Description

This PR moves the SignalInfo class from ophyd devices to BEC core and inspects the devices upon request to broadcast a runtime snapshot of the signal info per scan. This is the first step towards a more general support of acquisition groups and aliases in BEC signals.

[Copilot]

Pull request overview

This PR introduces a core, versioned representation of BEC signal metadata (SignalInfo) and adds a scan-time mechanism to broadcast a runtime snapshot of signal info for all devices locked by a scan, published by the device server to a dedicated Redis stream endpoint.

Changes:

• Add SignalInfo and BECSignalInfoMessage to bec_lib.messages and register a new bec_signal_info stream endpoint.
• Trigger a new device-server instruction (broadcast_bec_signal_info) after the scan stage step (direct-scan lifecycle) to request a signal-info snapshot.
• Implement device-server handling for broadcast_bec_signal_info and publish BECSignalInfoMessage updates to MessageEndpoints.bec_signal_info().

Reviewed changes

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

Show a summary per file

File	Description
bec_server/bec_server/scan_server/scans/scan_actions.py	Adds an internal helper to send a broadcast_bec_signal_info device instruction for currently owned device locks.
bec_server/bec_server/scan_server/direct_scan_worker.py	Calls the new broadcast hook after the stage lifecycle step in direct scans.
bec_server/bec_server/device_server/device_server.py	Adds instruction routing + implementation to collect BECMessageSignal.signal_info and publish a BECSignalInfoMessage to a Redis stream.
bec_lib/bec_lib/messages.py	Adds SignalInfo and BECSignalInfoMessage to the shared cross-service message contract and registers the new device instruction action.
bec_lib/bec_lib/endpoints.py	Adds MessageEndpoints.bec_signal_info() for publishing signal-info snapshots.

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[codecov]

Codecov Report

❌ Patch coverage is 89.74359% with 8 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...c_server/bec_server/device_server/device_server.py	82.60%	3 Missing and 5 partials ⚠️

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