[Widget] Spinner / progress bar / status line for long-running commands

[fissible]

Source: external review report, 2026-08-24 (notable exclusion #1)

Gap

CLAUDE.md's vision lists "progress bars, spinners, status lines" under Feedback. Alert and toast shipped; spinners and progress didn't. For a library whose consumers are deploy/ops scripts, a long-running-command progress primitive is arguably the most-wanted missing piece.

What it needs

• shellframe_spinner 'msg' -- cmd args… — runs the command, animates on /dev/tty, returns the command's exit code (preserves the $()/exit-code contract; stdout of the command passes through)
• shellframe_progress <current> <total> ['label'] — inline bar, idempotent redraw on the same line; callable in a loop
• shellframe_status 'text' — single-line status region for the v2 runtime (bottom row), updated without full redraw
• Respect SHELLFRAME_TPUT_OK / non-tty (degrade to plain text lines)
• Bash 3.2 clean; spinner animation via background subshell + trap, cleaned up on INT/TERM

Tests

• ptyunit: spinner wraps sleep 0.3; exit 3 → exit code 3, spinner frames observed, line cleared
• Unit: progress bar widths at 0/50/100%

Effort: M
Deps: none. Nice-to-have after #53 (theming) lands (colors).

[fissible]

Shipped in src/widgets/spinner.sh: shellframe_spinner (exit-status/stream-preserving wrapper), shellframe_progress (idempotent inline bar), shellframe_status (single-line repaint). Non-tty degradation per spec; bash 3.2 clean (matrix 3/3).

Deferred to follow-up (noted for PM): wiring a v2-runtime region variant of shellframe_status into the shell footer system — the standalone primitive ships now; runtime-region integration pairs naturally with #53 theming.