feat(tui): render hotbar in sidebar

[reidliu41]

Summary

Ref: #2065
Part of #2061

This adds the sidebar rendering layer for the Hotbar work:

• load resolved hotbar bindings from config/defaults into app state
• render the Hotbar panel at the bottom of the right sidebar
• show slots in compact two-row layout
• highlight active slots and keep unknown configured actions visible
• keep narrow sidebar rows within available width so later slots do not wrap or get clipped

This PR only adds the visible Hotbar panel. Key dispatch for 1-8 / Alt+1..8 remains a separate follow-up.

Testing

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets --all-features
• cargo test --workspace --all-features

Checklist

• Updated docs or comments as needed
• Added or updated tests where relevant
• Verified TUI behavior manually if UI changes
• Harvested/co-authored credit uses a GitHub numeric noreply address

[greptile-apps]

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[gemini-code-assist]

Code Review

This pull request introduces a configurable hotbar panel at the bottom of the TUI sidebar. It resolves hotbar bindings from the configuration, splits the sidebar layout vertically to allocate space for the hotbar when the terminal height is sufficient, and renders the hotbar slots with active/inactive states and custom labels. The review feedback suggests two improvements in crates/tui/src/tui/sidebar.rs: first, using unicode_width::UnicodeWidthStr::width instead of standard Rust formatting padding to prevent layout overflow when hotbar labels contain double-width characters or emojis; second, avoiding unnecessary cloning of binding.label by using .as_ref() and .cloned() during the filtering step.

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[gemini-code-assist]

Using Rust's standard formatting width specifier (e.g., {text:<cell_width$}) pads based on the number of Unicode code points (char count) rather than the actual visual display width. If the hotbar action labels contain double-width characters (such as East Asian characters or emojis), this will cause the padded cells to exceed cell_width in visual width, leading to layout overflow or clipping in the sidebar.\n\nWe can resolve this by calculating the visual width using unicode_width::UnicodeWidthStr::width and manually extending the string with the correct number of spaces.

            let mut padded = truncate_line_to_width(&format!("{}:{label}", cell.slot), cell_width);\n            let text_width = unicode_width::UnicodeWidthStr::width(padded.as_str());\n            padded.extend(std::iter::repeat(' ').take(cell_width.saturating_sub(text_width)));

[gemini-code-assist]

Avoid cloning the optional binding.label string unnecessarily. We can use .as_ref() to filter the label and only clone it (.cloned()) if it is present and non-empty.

            let label = binding\n                .label\n                .as_ref()\n                .filter(|label| !label.trim().is_empty())\n                .cloned()

[Hmbown]

Merged to main — thanks @reidliu41. Retargeted from the stewardship branch since your fork point was already contained in main. Key dispatch (1-8 / Alt+1..8) green-lit as the follow-up slice; part of the #2061 Hotbar program.