VMXm: fast grid scans

Umbrella issue for fast grid scans on VMXm - subtickets to be created as work becomes clearer.

Simple fast grid scans, 2D scan at a single rotation angle, heatmaps not needed in GDA but would be liked in ispyb.

Queries/outstanding work:
- Fast shutter control currently being done in geobrick motion program, may make more sense for GDA/bluesky to do this.
* Two shutters - fast & slow - need coordinating correctly.
- Still need to figure out exactly how VMXm's zebra is set up and demo a fast grid scan running & triggering the detector but setting everything up manually rather than through GDA/bluesky.
* Scientist to add meeting next week about this.
- Metadata:
* `aperture_scatterguard`, `flux`, `s4_slits`, `undulator`, `xbpm` - not required or don't make sense for VMXm.
* `backlight` just needs moving out, nothing else.
* `attenuator` would be good to include on VMXm.

VMXm scientists have said they would *like* some basic functionality by 20th Nov as they have scheduled an experiment that would benefit from this...

**Edit RT 2026-05-05:**
PRs:
* DiamondLightSource/mx-bluesky#1623
* DiamondLightSource/dodal#1925
* DiamondLightSource/mx-bluesky#1636
* DiamondLightSource/mx-bluesky#1653
Issues:
* DiamondLightSource/mx-bluesky#1763
* DiamondLightSource/mx-bluesky#1764
* DiamondLightSource/mx-bluesky#1765
* DiamondLightSource/mx-bluesky#1766
* DiamondLightSource/mx-bluesky#1768
* DiamondLightSource/mx-bluesky#364
* DiamondLightSource/mx-bluesky#306
* DiamondLightSource/mx-bluesky#288
* DiamondLightSource/mx-bluesky#1248 - a number of hotfixes applied in scratch folder that should be merged
* https://github.com/DiamondLightSource/mx-bluesky/issues/1634

JIRA issue with longer-term gridscan goals: https://jira.diamond.ac.uk/browse/VMXM-200

**Comment history below this initial summary retained only for historical purposes, all current work to be tracked in GH issues temised above.**