Sidebar: stack multiple footer actions vertically (wide plugin footers get squeezed)

[AndyPBI]

Problem

When multiple plugins register into the sidebar.footer.action seat at once (for example dsh-knowledge's icon button next to dsh-workvista's project worktable), the seat lays its occupants out in a horizontal flex row (.footerActions in packages/client/ui-sidebar/src/client/SidebarRoot.module.css). A wide plugin footer that requests width: 100% (the worktable) loses its space next to sibling buttons, and the sidebar footer becomes cramped.

Suggested fix (CSS-only, no slot/API changes)

Stack the seat vertically:

.footerActions {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

• Every footer action gets its own full-width row.
• In collapsed (rail) mode the same column direction carries over: footer icons stay vertically centered, consistent with the rail's existing vertical icon language.
• .settingsArea and the owner/slot contracts are untouched; each occupant still owns its button geometry.

Verification

• pnpm vitest run packages/client/ui-sidebar → 28 test files / 241 tests passed (including the sidebar snapshot suite).
• Manual, in a Web profile with both dsh-knowledge and dsh-workvista installed: footer actions stack vertically; the worktable keeps its full width. The client-hmr stat-poll chain hot-swaps the rebuilt ui-sidebar bundle without a server restart.

Patch

Branch: https://github.com/AndyPBI/deepseek-harness/tree/fix/sidebar-footer-actions-vertical
Commit: AndyPBI@e7b5e49f99

One file, +5/-1. The team is welcome to take it as-is or adapt it to DSH conventions.