Feature: Configurable tmux-style status bar

[blankjul]

Problem

Coming from tmux, one thing I miss in Herdr is a status bar. tmux lets you put
whatever you want in status-left / status-right — session name, git branch,
a clock, system stats via #(shell) — and style it inline. Herdr has the tab
bar and sidebar, but no dedicated, user-configurable line for that kind of
at-a-glance info.

Proposal

An opt-in status bar configured under [ui.statusbar], driven by tmux-style
format strings so existing tmux status snippets mostly carry over:

• #{name} — Herdr variables (workspace_name, tab_name, branch,
  host_short, counts, active agent / agent_state, …)
• #[fg=…,bg=…,bold,dim] — inline styling; #[default] resets
• #(shell command) — command output (opt-in, refreshed on an interval)
• %H, %M, %d, … — strftime-style local time; ## is a literal #

left / center / right zones, position = "top" | "bottom", base bg/fg.
Off by default, so nothing changes unless you turn it on.

Example (what I'm running)

[ui.statusbar]
enabled  = true
position = "top"
shell    = true
interval = 3
bg = "#44475a"
fg = "#f8f8f2"
left   = ''' #[bold]#{host_short}#[default]   #[fg=#bd93f9]#{branch}#[default] '''
center = ''' #[bold]%H:%M '''
right  = ''' #[fg=#50fa7b]CPU #(awk -v n=$(nproc) '{printf "%.0f%%",$1/n*100}' /proc/loadavg)#[default]    #[fg=#f1fa8c]MEM #(free -m | awk '/Mem:/{printf "%.1f/%.1fG (%.0f%%)",$3/1024,$2/1024,$3/$2*100}')#[default]    #[fg=#ff79c6]DISK #(df -h / | awk 'NR==2{printf "%s/%s (%s)",$3,$2,$5}')#[default] '''

Renders (top row, full width):

 myhost   main              14:32              CPU 40%    MEM 4.8/15.5G (31%)    DISK 123G/227G (58%)
 └ left                     └ center           └ right

Implementation

I have this working on a branch:
https://github.com/blankjul/herdr/tree/feat/statusbar
(diff vs upstream:
master...blankjul:herdr:feat/statusbar)

• New [ui.statusbar] config; StatusbarConfig mirrors the existing config
  structs, and the format parser/renderer is its own src/ui/statusbar.rs.
• Layout carves a full-width row in compute_view (panes shrink to fit); a
  render_statusbar draws it. Parsing is pure; #(shell) output is refreshed
  during the compute pass so render stays side-effect-free.
• Kept entirely in the TUI/client layer per the runtime/client boundary guidance
  — no server/protocol changes.
• Local time via a small platform helper; libc (already a dep) resolves the
  system timezone.
• just check passes (unit tests for the parser/render + Linux and Windows
  clippy), and the config-reference is updated for the new keys.

[stewartcelani]

I also just migrated from tmux and this is the one thing I miss from tmux. Having my servers CPU, RAM, DISK %, backup, RAID status and even live visitors per site was great. Please consider implementing. :)

[Mingzefei]

We neeed this!

[cperalt]

Bumping as well! Sidebar is really awesome but when its hidden i have a tendency to loose track of what workspace I am on

[eduardoarandah]

Great job on the bottom tabs!

I'm almost switching from tmux

+1 on the custom spaces, I like having "[ session name ]" on the left and some custom tmux notifications on the right, but hey.. maybe somebody wants a button to launch lazygit, idk, just give us a way to insert actions

.tmux.conf

# notifications on the right, test : tmux set -gq @notification "Your process stopped successfully"
set -g status-right '#{?@notification,  #{@notification}  ,}'
set -g status-interval 1
# click to dismiss
bind -n MouseDown1StatusRight set -gu @notification

[ogulcancelik]

this is largely covered via #2586

it's not a separate bar but enables you to customize the tab bar with custom scripts and default options. will be available in the next release.

feel free to move new discussion if you need more features on the tab bar!