fix(planning): decide-pane layout and accessibility papercuts on the interview page #7970

This was generated by AI during attend-queue.

Refs: #6053
Depends on: #7967

Agent Brief

Type: Bug
Summary: The question pane shows the recommendation once, expanding Why does not move Details, side panels default to pinned on wide screens, Finish is secondary while questions are open, and every button has an accessible name.

Current behavior:

• The recommendation appears twice (green card and the Rec row), plus an auto Claude asked thread line repeating the label; the header repeats stage and group when they match.
• Expanding Why shifts the Details disclosure under the next click.
• Side panels overlay the decide and Talk controls by default (pinned defaults false).
• The summary's Finish: export and end the session uses the primary style while questions are open.
• One button has no text, aria-label or title.
• Q5 (decide list cap) was fixed by fix(planning): rebalance the interview page layout and add a someone-else-decides deferral #7278, verified at 1440x900 only.

Desired behavior:

• The full recommendation text appears once in the question pane; the auto thread line that repeats the label is gone; stage and group collapse to one when equal.
• Expanding Why leaves the Details control where it was (space reserved, or Why and Details rendered so one does not push the other).
• At a viewport 1200 px wide or wider, with no stored preference, panels open pinned; Pin is labelled visibly; a stored pin choice still wins.
• While the outstanding count is above 0, Finish uses a secondary style and stays enabled (rule R4); at 0 it is primary.
• Every button has an accessible name; label text colors meet WCAG AA (4.5:1) in both themes.
• At 1568x744 the full Rec text and every alternative are visible in the decide list without inner scroll.

Key interfaces:

• Page render functions for the question pane, the summary's Finish button and the fly-out panel default (S.pinned initial value).
• Theme color tokens for label text.

Acceptance criteria:

• Playwright UI cases in the surface suites cover: recommendation text occurs once; the Details bounding box is unchanged after expanding Why; panels are pinned by default at 1280 px with no stored choice; Finish is not primary and stays enabled with open questions; no button lacks an accessible name; the decide list has no inner scroll at 1568x744. Check: the PR's CI runs plugins/planning/surface/surface.test.sh with the browser suites and it passes. A local SKIP without playwright-cli is not a failure.
• The PR body names each changed label color with its contrast ratio, computed from the token hex values (WCAG relative-luminance formula), and each ratio is at least 4.5:1 in both themes. Check: the reviewer recomputes one.
• A planning fragment exists (scripts/new-changelog-fragment.sh planning patch), and scripts/check-changelog-fragments.sh --check passes.

Out of scope:

• The header listening state (sibling item this follows, both edit the page).
• fix(planning): interview page visual audit follow-ups to #5569 #5795 and planning: show the whole recommendation in the interview page's Accept choice #5815 beyond the overlap named here.
• Narrow-viewport (820 px breakpoint) redesign and keyboard-navigation changes.

This was generated by AI during backlog shaping. Split from #6053; the owner approved filing it in an attended backlog-shaping session on 2026-10-18.