Animate the Todo task in progress with a spinner #222

Parent

Spec: ctui 0.5.0, sections "Spinner" (Implementation Decisions) and stories 21–22. Decided in the Todo spinner spike on 2026-10-09: prototype/todo-spinner (commit 6fa9e40).

What to build

In the Todo section, the task in progress shows an animated spinner in place of the fixed ◐, and waiting tasks show ⠶ in place of ○.

• In progress: frames ⠴ ⠦ ⠖ ⠲, one every 100 ms, in warning; the text stays the activeForm in main.
• Waiting: ⠶ in faint, text in muted. Done rows are unchanged (✓, muted).
• A new surface module ctui/plugins/todo/spinner.tsx (props { frames, ms, color }, frame index as local state, one surface.every started while state is undefined) animates on the surface's own frame clock, so the Sidebar doesn't redraw. The Todo view draws it as a Client with module="./spinner.tsx" (a literal) and key spinner-<item.id ?? index>, in a 1-cell Box, followed by a Text with a space and the task text, inside one row Box.
• Widen the Sidebar plugin's ui type in ctui/plugins/plugin.ts to the Sidebar's terminal/desktop table so the view gets Client without a cast.
• The spinner isn't pressable, so it stays a Client while the Pane is focused. The folded summary stays text.

The spike's spinner.tsx is the starting point; its sample lists, the 40-row cap and the PROTOTYPE comments in todo/index.tsx don't ship.

Branch: bugfix/todo-spinner from release/0.5.0, with its pull request into release/0.5.0 once the release pull request into main is open (AGENTS.md, Branches).

Acceptance criteria

• todo-sidebar.test.tsx: the task in progress draws through the spinner.tsx Client, first frame ⠴ in warning, with its activeForm in main; waiting tasks draw ⠶ in faint; done rows unchanged. tests/clients.tsx gains a spinner.tsx stub.
• A unit test for spinner.tsx: each every tick steps to the next frame and wraps after ⠲.
• No PROTOTYPE comments or sample lists remain; Todo's cap is 8.
• MEMORY.md, "The todo Sidebar plugin turns the task tools on by default": Guidance names the rows (✓ muted, the ⠴⠦⠖⠲ spinner at 100 ms in warning drawn by the spinner.tsx Client on its own frame clock, ⠶ faint for waiting); Reason gains the spinner spike.
• docs/design/sidebar.html draws the in-progress row as ⠴ and waiting rows as ⠶; the PNGs are re-exported.
• docs/testing/live-checks.md: the Todo row's glyphs read ⠶ in subtle and a spinner turning through ⠴ ⠦ ⠖ ⠲ in warning; a new row: with the Pane focused (ctrl+x tab) the spinner keeps turning, and a /theme switch recolors it within 0.5 s. Both run and passed on 2.1.292; the PR says so.
• node scripts/check.ts exits 0.

Blocked by

• None (can start once the release/0.5.0 pull request is open)