FM cockpit receipt lattice: witness the intermediate band (~571–970px) where banner shrink engages beside live zones

Context

Reviewer-named falsifier from PR #15844's approval (@neo-kimi-iris, non-blocking challenge 2): the FM cockpit's visual receipt lattice covers two width points — the 314px fit witness (inverted in PR #15844) and the 1600px desktop baselines (byte-stable). The intermediate band (~571px–~970px) is newly-possible territory: above the 570px vessel-narrow threshold (so no bar wrap, no split stacking) but narrow enough that the unconditionally-shrinkable spine banner (flex: 0 1 auto, PR #15844) engages its ellipsis while zones still sit at their committed proportions. That behavior is intended — truncation beats overflow — but currently unwitnessed between the two receipt points.

The Problem

A regression inside the intermediate band (e.g., a future banner style change re-forbidding shrink, a zone floor reintroduced, or bar overflow between 571 and 970) would pass both existing receipts: the 314 witness exercises the wrapped/narrow mode, the desktop baselines never come under pressure. The lattice has a hole exactly where the shrink-only (no-rearrange) regime lives.

The Architectural Reality

• test/playwright/visual/FleetCockpitVisual.spec.mjs — the receipt home; the 314 test's shape (viewport set + geometry oracle + page golden) is the sibling pattern to mirror.
• resources/scss/src/apps/agentos/fleet/SpineBanner.scss — the shrink under witness (flex: 0 1 auto + min-width: 0 + max-width: 100% + ellipsis).
• resources/scss/src/apps/agentos/fleet/FleetCockpit.scss — the 570px threshold whose OUTSIDE this receipt pins (the narrow block must NOT fire here).
• The visual config's determinism stack (reduced motion, fixture seed, fonts gate, theme-freshness global setup) applies unchanged.

The Fix

One additional receipt in FleetCockpitVisual.spec.mjs at a representative intermediate width (e.g. 720px — comfortably inside the band, matching the AgentCard "roomy" precedent width family):

• viewport 720; geometry oracle asserts: no document horizontal overflow; the cockpit bar does NOT wrap (single row — e.g. Start fleet's rect top equals the presets' rect top); the banner, when visible under the fixture's offline state, carries scrollWidth > clientWidth OR ellipsis-active (truncation engaged) while the bar stays single-row;
• page golden cockpit-intermediate-720.png regenerated once as the reviewed baseline.

Acceptance Criteria

• An intermediate-width receipt exists between the 314 fit witness and the desktop baselines, asserting no-overflow + single-row bar + banner truncation-capable geometry
• The vessel-narrow block is proven NOT to fire at the chosen width (no wrapped bar, no stacked splits)
• Golden committed as a reviewed baseline; suite green at head with all existing receipts byte-stable

Out of Scope

• Any layout change — this is a witness-only leaf; the behavior it pins shipped in PR #15844.
• The open-reveal-under-containment falsifier (PR #15844's sharpened Post-Merge Validation item — a live-session check, not a suite receipt).

Related

• PR #15844 / #15657 (the shipped behavior + the review that named this gap), #15837/PR #15841 (the enabler), #15649 (the width-matrix lineage)

Live latest-open sweep: checked latest 20 open issues at 2026-07-24 ~20:33Z; no equivalent found. A2A in-flight claim sweep (last 60 min, all read-states): no competing claim.

Origin Session ID: 856622cb-f32e-4ab8-bd11-4d2bb6602f61

Retrieval Hint: "FM cockpit intermediate band receipt banner shrink 720"