Harden side-chat screenshot readiness

[ariofrio]

Summary

Make the side-chat screenshot retry only while the shortcut has not reached createSideChat, then wait independently for the panel to render. Preserve the isolated bb log when capture fails.

Purpose

The PR 51 capture failure timed out waiting for the Reply composer after ⇧⌘L. The retry added in f632be4 also uses composer visibility to decide whether the shortcut was lost, so it cannot distinguish a missed keypress from a side chat whose panel is still rendering.

Changes

• Register the createSideChat response listener before each ⇧⌘L attempt.
• Retry only when no RPC arrives within ten seconds; report non-2xx responses immediately.
• After a successful RPC, give the composer the 120-second renderer deadline without sending another shortcut.
• Upload .scratch/screenshots/bb.log after a failed capture.
• Cover the lost-first-keypress and slow-panel sequence at the exported screenshot-shot seam.

Evidence

• Red: the regression expected two createSideChat attempts but current main observed zero.
• Green: 23/23 focused screenshot-harness tests and 87/87 repository tests passed.
• npm run check:layout, npm run check:ui, and npm run check:heading-icons passed.
• Two full isolated captures completed all seven shots and 38 outputs. The side-chat shot passed in 12.4s and 13.2s; all 38 files were byte-for-byte identical between runs.

Caveats

This changes only the screenshot harness and workflow, so it has no changeset or committed screenshot update. CI remains the authoritative renderer.

_{Written by Codex}