fix: keep the sidebar agent badge readable and drop spinner glyphs from titles

[arzafran]

What this does

The agent badge in a sidebar row ("Needs input", "Working", "Done") no longer gets squeezed down to an unreadable red "!" when the title is long. The title now shortens with an ellipsis instead. Titles also stop showing the spinner character Claude Code puts at the start of its terminal title, since the badge already shows that state.

Summary

• Sources/TabItemView.swift: the badge gets .fixedSize and a higher layout priority than the title, so SwiftUI truncates the title first.
• SidebarTitle.strippingLeadingStatusGlyph drops one leading text symbol plus its space ("◐ Fix tests" becomes "Fix tests"). Letters, punctuation and emoji like "🚀" are left alone, and titles the user renamed by hand are never touched.

Test Plan

• reload.sh tagged build succeeds; structural budgets pass
• In the tagged app, a terminal titled "◐ CPU usage monitoring" with a blocked status shows "CPU u…" plus the full red "Needs input" badge at the narrowest sidebar width
• CI: ProgramStatusStoreTests/testSidebarTitleStripsLeadingSpinnerGlyphOnly passes