fix(planning): keep unpinned Notes and Activity flyouts off the interview note box at 1440 px #8083

Refs: #7756

Agent Brief

Type: Bug
Summary: At 1440x900 an unpinned Notes or Activity flyout no longer covers the note box, Ask Claude or Rephrase.

Current behavior:
At 1440x900, opening the Notes or the Activity flyout without pinning it covers the note box and the Ask Claude and Rephrase buttons, so the user cannot write a note while reading the panel. The sticky decide bar measured 374 to 435 px tall at 1440x900 before #7278 rebalanced the layout.

Desired behavior:

• At 1440x900, with Notes or Activity open and unpinned, the note box, Ask Claude and Rephrase stay fully visible and clickable. The agent chooses how: a narrower flyout, a reflowed detail column, or another layout.
• A pinned panel behaves as it does today.
• The sticky decide bar is re-measured at 1440x900. Change it only if it still hides the question title, and record the height in the PR either way.

Key interfaces:

• The flyout panel render for Notes and Activity, unpinned versus pinned (the Pin control).
• The note box and the Ask Claude and Rephrase controls in the question detail.
• The sticky decide bar.

Acceptance criteria:

• The diff adds a check to the question-page UI suite (plugins/planning/surface/tests/ui_page.js): at 1440x900, with Notes open unpinned and again with Activity open unpinned, the bounding boxes of the note box, Ask Claude and Rephrase do not intersect the flyout's bounding box.
• The PR body records the decide bar height at 1440x900 and says whether it changed.
• scripts/check-changelog-fragments.sh passes, with one planning patch fragment added.
• CI's test-bash passes on the PR. It runs plugins/planning/surface/surface.test.sh with its browser suites.

Out of scope:

• Jump to the newest note and collapsing older notes (sibling item).
• Layout at 390 and 425 px: id chips, the Summary table, the header (sibling item).
• Mobile rail tap behavior (fix(planning): rebalance the interview page layout and add a someone-else-decides deferral #7278), contrast and touch targets (fix(planning): fix interview page contrast, touch targets and unexplained labels #7755).

Refs #7756

This was generated by AI during backlog shaping. Split from #7756 so each piece fits the lane's run time; the owner approved this split in an attended backlog-shaping session on 2026-10-18.