[FEATURE] Anchor bar to one end of an edge (corner bar)

[XimoCP]

Submission checklist

• I have searched existing issues and confirmed this has not been requested before.
• I have checked existing pull requests for similar changes.

Feature type

Configuration / customization

Feature summary

Add a per-bar alignment option so a bar can be pinned to one END of its edge (top-left, top-right, bottom-left, bottom-right) instead of always being centered on the edge. Combined with auto-resize (#3527), this allows a small "corner bar" whose background ends where the content ends and grows from the corner of the screen.

Motivation / use case

Today position only supports top/bottom/left/right and the bar surface is always centered on the edge; margin_ends insets BOTH ends symmetrically, so a shrunken bar stays centered. Users who want a minimal pill in a corner (e.g. bottom-right) cannot get it. The workaround — a full-width transparent bar with content in a single lane — leaves an invisible but clickable full-edge strip.

Proposed solution

Add an alignment/anchor option per bar, e.g.:

[bar.corner]
position = "bottom"
align    = "end"   # start | center | end — default "center" (current behavior)

start hugs the left end of a horizontal bar (or top end of a vertical bar); end hugs the right/bottom end. When combined with auto-resize (#3527) the background would cover only the content, producing a small pill growing from the chosen corner.

Design question for maintainers: should a corner bar still reserve the full edge exclusive zone, or only the corner region?

Alternatives considered

• Transparent full-width bar + content in a single lane: works visually, but the whole edge stays clickable (see [FEATURE] Bar click-through to pass pointer events through empty areas #3324 for click-through requests).
• Desktop widgets: free placement, but not a real bar (no exclusive zone, no attached panels, no auto-hide).
• Plugins: cannot change the built-in bar anchoring (only add widgets).

References / related projects

• [FEATURE] auto-resize bar width to content #3527 (auto-resize bar to content — complementary)
• [FEATURE] Bar click-through to pass pointer events through empty areas #3324 (bar click-through for empty areas)
• The dock already anchors to a single edge and sizes to content, a good precedent.

Additional context

Tested on Noctalia v5.0.0. The align key would need to be added to BarConfig + monitor overrides + Settings UI + schema tests.