feat(workspaces): support min_workspaces for dynamic outputs

[Ashur-D]

Summary

Adds a min_workspaces configuration option (integer from 1 to 64, default 1) to [workspaces].

When using dynamic workspaces on an output:

• Initial workspace resolution guarantees at least min_workspaces are created.
• During dynamic reconciliation (WorkspaceGroup::reconcileDynamic()), empty workspaces with indices < min_workspaces (0-based) are retained rather than pruned.
• Workspaces beyond min_workspaces continue to be dynamically created and destroyed as views open and close.
• Runtime changes to min_workspaces trigger workspaceInventory and workspaceLayout refreshes.

Motivation

Users who enjoy dynamic workspaces often still want a persistent minimum set of workspaces (e.g. 3, 4, or 5) always available and visible in their status bar, dock, or overview without having to switch completely to static workspace rules.

Type of Change

• Bug fix
• New feature
• Breaking change
• Refactoring
• Build / packaging
• Documentation

Related Issue

Testing

• Added unit tests:
  • tests/unit/config_load.cpp: verifies loading and clamping of min_workspaces (clamp to 1 min, 64 max).
  • tests/unit/config_resolve.cpp: verifies resolveWorkspacesForOutput produces at least min_workspaces on dynamic outputs.
  • tests/unit/config_change.cpp: verifies ConfigEffects::between reports workspaceInventory and workspaceLayout when min_workspaces changes.
• Automated tests passed:
  • meson test -C build --no-suite umbrielfx (all 35/35 unit tests passed).
• Code formatting verified with clang-format.

Manual Coverage

• Tested in a native Umbriel session
• Tested with native Wayland applications
• Tested with the scrolling layout
• Tested with the dwindle layout

Screenshots / Videos

Checklist

• This PR is ready for review, or it is marked as Draft.
• This change fits SCOPE.md, or its scope was agreed in an issue or on Discord first.
• I read and followed the relevant guidance in CONTRIBUTING.md.
• I ran just format, or this PR has no C++ changes.
• I ran the relevant build, test, lint, or verification commands, or explained why they were not run.
• I functionally verified compositor behavior where automated checks are insufficient.
• I self-reviewed the changes.
• I checked for new warnings or errors.
• I updated docs/ and examples/config.toml, or this PR does not change user-facing configuration or behavior.
• I used canonical names for config keys, IPC actions, paths, and identifiers.

Additional Notes

None.

[ItsLemmy]

Thanks for the PR, as you pointed on Github yesterday it was a bit of a shortcut to get it working.
I rewrote a more global approach with "min_workspaces" per output, so people with multi monitors can profit from the feature. Thanks none the less for your input! every contribution matters.

[ItsLemmy]

Implemented in c34d7b9