[idea] Allow compact worktree indentation with single-line Space rows

[chrishas35]

idea / problem

Herdr supports customized Space sidebar rows. For example, the default layout places repository and branch information on separate lines:

[ui.sidebar.spaces]
rows = [
  ["state_icon", "workspace"],
  ["branch", "git_status"],
]

With that layout, the existing worktree connector indentation fits naturally into the multi-line entry.

A compact single-line layout is also supported:

[ui.sidebar.spaces]
rows = [
  ["state_icon", "workspace", "branch", "git_status"],
]

With this layout, worktree children retain the same fixed indentation:

• project · main                                 ▾
   └─ ○ feature-branch

The deeper prefix is more noticeable in a single-line layout and leaves less room for the worktree label.

This is a follow-up to the single-line Space layout discussed in #873 and the worktree tree layout introduced through #1694 / #1873. Both features work well independently, but their combination leaves a relatively wide fixed prefix on worktree-child rows.

requested change

Please consider making worktree-child indentation configurable, without changing the existing default.

For example:

[ui.sidebar.spaces]
worktree_indent = 1

This could allow a compact layout such as:

• project · main                                 ▾
 └─ ○ feature-branch

Alternatively, Herdr could derive a more compact indentation automatically when Space entries use a single configured row.

why you want this

Configurable indentation would let users take advantage of the documented single-line row layout without losing as much horizontal space to the worktree tree prefix.

The current indentation could remain the default for the standard two-line layout. This would preserve the existing visual design while allowing denser sidebars to remain readable when workspace or branch labels are longer.