Tray layout: zoom<->auto-fit scrollHeight mismatch (tall cards clipped at zoom >100%) + proof-harness anchor overflow

[Finesssee]

Tray layout bugs surfaced by the #261 repro rig

While running the seeded-repro investigation for #261 (seeded proof harness driving the ambient Codex provider card), two layout bugs in adjacent code turned up. Neither reproduces #261, both are confirmed numerically. They are tracked here so they aren't lost when #261 closes.

1. useTrayPanelLayout measure uses zoom-invariant scrollHeight while TrayPanel applies CSS zoom

• apps/desktop-tauri/src/surfaces/TrayPanel.tsx applies style={{ zoom: trayScale }} on the rendered surface; useTrayPanelLayout.measure / auto-fit sizes the WIN32 window from DOM metrics (body scrollHeight + bottom offsets).
• Measured: body scrollHeight is IDENTICAL at tray zoom 100/150/200 (800-ish px in all runs — see probe in proof-261-seed/zoom*/probe trace), but rendered visual height scales with zoom. Outcome: at tray zoom >100% the window is sized to the PRE-zoom height and tall cards are clipped below the fold; a horizontal scrollbar appears mid-flyout.
• Repro path: apply tray zoom 150% in Settings -> Menu -> Tray panel scale (or the settings preset), open tray flyout with a tall card (e.g. Codex with long top-model + reset credits) and observe the clipped bottom content + horizontal scrollbar.
• Suspected fix area: apps/desktop-tauri/src/hooks/useTrayPanelLayout.ts measure/apply block — multiply measured content height by the active zoom factor before clamping (or compute content height in post-scale px).
• Evidence: proof-261-seed/zoom150-ds1/, proof-261-seed/zoom200/ capture folders in run 2026-08-06 (rects.json, panel_series.json, screenshots).

2. Proof-harness anchor point overflows work area on tall auto-fit flyouts

• apps/desktop-tauri/src-tauri/src/proof_harness.rs anchor positioner anchors the flyout at y=252 for the default initial size; after auto-fit settles a tall panel (≥ ~790px) the bottom edge drops below the 1040px work bottom on 1920x1080 displays, clipping content against the screen edge (harness-only behavior).
• Not user-facing under normal use — impact scoped to proof runs; fix entails re-anchoring the flyout to the selection nearest the bottom edge (justified-above-taskbar) when measured height > available space, or clamping auto-fit max-height to workBottom - anchorY - inset and letting content scroll.
• Evidence: proof-261-seed/zoom200/rects.json (settled rect bottom y > work bottom).

Both findings are independent of the #261 Codex-tab resize-loop investigation; their triggers are orthogonal (static tall content / static anchor math).

Note: the first finding's measured probe values come from a temporary resize probe injected for investigation (cleanly reverted; no main-line diff remains). The second is observable WIN32-geometry behavior.

[Finesssee]

Fixed in #266 (squash-merged as 02971a7).

1 — zoom × auto-fit mismatch: useTrayPanelLayout auto-fit measures through a new scaledContentHeight(rawHeight, zoom) helper applied at both derivations (scrollHeight/rect seed + bottom-edge walk) before the existing min/max clamp — the window is now sized in post-zoom px. useTrayPanelController passes the active trayScale. Plus min-width: 0 re-asserted on .menu-surface--tray (cascade-order override): the base 260px floor was zoom-multiplied (390px at 150%), causing the horizontal scrollbar. Test: TrayPanel.test.tsx commits 328×762 from raw 505 at 150% (round(505×1.5)+4) and still caps at the 884 work-area clamp for raw 700.

2 — proof-harness anchor overflow: proof_window_position now justifies the anchor with proof_anchor_y = anchor.min(work_bottom − 8 − max_settle) (max settle = frontend's 920px auto-fit cap), so even the tallest settle keeps its bottom edge at work_bottom − 8. Anchors that already fit are unchanged. (set_max_size was tried first — Win32 ignores it for programmatic setSize.) Test: tall_panel_bottom_edge_never_passes_work_bottom_minus_inset asserts 252 → 112 on the 1080 rig and bottom == 1032.

Live CUA verification (1920×1080, work area 1920×1040, tray zoom driven to 150% via the footer slider and persisted trayScalePercent: 150, CODEXBAR_PROOF_MODE=trayPanel + seed of the proof-261-seed/full shape):

• Settled rect (1580, 112, 328, 920) → bottom edge 1032 = 1040 − 8 inset ✓ on screen
• DOM: bodyScrollWidth == clientWidth == 328 → no horizontal scrollbar; footer bottom 841 ≤ 920 inner height → card's bottom content (cost block + footer through Quit) fully visible (was clipped pre-fix)
• Screenshot: proof-265/zoom150-tallcard-fixed.png; rects: proof-265/zoom150-tallcard-fixed-rects.json; observation: proof-265/zoom150-tallcard-fixed-observation.json

Gates on the committed tree: tsc clean, vitest 227 passed, cargo test 332 passed, clippy -D warnings clean, rustfmt clean; CI "Local check" green.