#32669 Agent pane: the recap card and the host's line on the composer card's edges (carries #28587)

Carries the part of #28587 that base doesn't cover yet. Leo, 2026-10-30, on the agent pane's bottom stack:

"the stupid right indent misalignemnt"

#28587's goal: every part over the composer shares the composer box's left and right edges at every width (including the narrow outset and --cv-inset-end) and the box's radius token. Base has since done this for the running tray (#28533, #29264, #29885, #31424: --acpmux-tray-outset, the radius token, the joined glass) and removed the PR chips (#29614), so #28587's branch no longer merges. What it still carried of its own was the recap card and the host's line; this PR ports only those onto base's design.

What changed

• bottomStack.css: .acpmux-dock defines --acpmux-stack-outset, the composer's 8px narrow outset (same 297.5px clamp the tray uses), for the other parts on the card's edges. The percentage resolves at the part using it.
• Recap card (summary.css): right edge takes --cv-inset-end (it used --cv-inset on both sides, so it stood inside the column while the computer use preview pulls the column's end in), both edges take the narrow outset, and the card takes --acpmux-composer-radius (fallback 11px, as the tray) instead of a fixed 12px.
• Host's line (styles.css): the same edges.
• Vertical spacing is unchanged: the recap's 6px and the host line's 8px under them stay. Joining the recap to the composer as one glass, as the tray does, is a separate design step.
• Test: agent-pane.bottom-stack-styles gains a recap variant (sessionStatus on, a turn ending on a question); test/agent-pane-bottom-stack-edges.test.ts checks the recap card's left/right against the composer card to 1px at 1100, 420 and 320px (320 puts the composer under its narrow outset).

Spec: design/running-tray.md (bottom stack); no settled design changes.

🤖 Generated with Claude Code

Agent session: agent session

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Summary by cubic

Aligns the recap card and the host's line with the composer card's left and right edges at every width in the agent pane's bottom stack, completing the part of #28587 that base's bottom stack work hadn't carried over.

• Adds --acpmux-stack-outset on .acpmux-dock (the composer's 8px narrow outset) so both parts follow the composer's edges the same way the running tray does.
• The recap card now takes --cv-inset-end on the right edge instead of --cv-inset on both sides, and its corner uses --acpmux-composer-radius (11px fallback) instead of a fixed 12px.
• Vertical spacing is unchanged: the recap's 6px and the host line's 8px padding stay.
• Adds a recap gallery variant and a test checking the recap card's edges against the composer's to 1px at 1100, 420, and 320px widths.