Problem / Background

In local view, the top metrics row under the host summary bar shifts left and right as live values change.

The affected row is the compact local-mode summary line that renders:

• CPU
• GPU
• RAM
• Pwr
• Tmp

When one metric crosses a digit boundary, neighboring segments move. Typical examples:

• 9.9% -> 10.0%
• 99.9% -> 100.0%
• 99°C -> 100°C
• 9.9W -> 10.0W
• RAM used / total strings changing visible width

This makes the local header look unstable even though the rest of the TUI is stationary.

Suspected Code Location

• src/ui/local_header.rs
• especially the formatting path around draw_metrics_line() and the per-metric helpers

Expected Behavior

The local header metrics row should have stable horizontal layout across refreshes.

• Each metric segment should reserve enough width for its value field.
• Braille sparklines should stay aligned frame-to-frame.
• One metric growing from 2 digits to 3 digits should not push the following metrics sideways.

Proposed Fix

Use fixed-width or explicitly padded value fields for each metric segment in the local header.

Examples:

• CPU/GPU percentage fields should reserve width for 100.0%
• temperature should reserve width for 100°C or a similarly safe upper bound
• power should reserve width for a stable watt display field
• RAM should reserve a stable used/total field width, or split/pad the numeric portion so the segment width is constant

If needed, compute display widths once and right-pad or left-pad before writing colored text.

Acceptance Criteria

• In local mode, the CPU/GPU/RAM/Pwr/Tmp row stays horizontally stable during refreshes.
• Transitions like 9.9 -> 10.0, 99.9 -> 100.0, and 99 -> 100 do not move neighboring segments.
• Braille sparklines remain aligned across refreshes.
• No regression in color rendering or metric content.
• cargo test and cargo clippy pass.

Notes

This is specifically about the local-mode compact summary header introduced by the local TUI redesign, not the lower Activity panel.