cast v0.6

cast 0.6.0

• Every existing next cycle gains prev, including layout, presets, camera
  anchors/shapes and Xorg monitors; camera aspect can cycle in both directions.
• New stage layout places the screen opposite the camera anchor, preserves both
  aspect ratios and naturally overlaps the sources when their sizes require it.
• Screen layers gain configurable borders and rounded corners; stage has its own
  screen size and margin. CLI, panel and config expose the controls.
• Screen/stage backgrounds can use a fresh blurred screen frame (default), a
  camera frame, a solid fill, or a shared linear gradient with two/three colors,
  adjustable angle and middle-stop position. Camera gradient mode shares these colors.
• Add an anchored transparent image logo and static text with a selected font,
  independent horizontal/vertical edge distances, size, color and opacity.
• Rounded screen masks use scanline spans; logos and static text are prepared
  once and reused while fresh blurred backdrops track each source frame.
• The panel keeps these controls in Source and Effects disclosures, with separate
  floating preview and output/privacy actions always reachable.

Runtime changes remain session-only. Composition controls never resume outputs or
change recording state. Stop cast before updating, then restart daemon and panel
from the same build. Arch x86_64 assets include Xorg, Wayland and panel support,
checksums, matching source and build provenance.