V2: Scroll the chat rail as one panel and pop workflow alerts from the bell

[Paul Lizer (paullizer)]

Summary

On the V2 chat page the rail kept its full height for the navigation and the admin's link groups, and the conversation list scrolled in what was left: two rows in a 720px window with two external links. Classic has scrolled its whole sidebar as one panel since 0.250.002 (#1098).

• Chat rail scrolls as one panel. With the rail expanded on the chat page, everything between New chat and the theme/account footer is now one scroll region. Reading down the list carries the navigation and External Links / Custom Pages out of view, and Search chats (plus the bulk-selection bar) is held right under New chat. The list goes from 2 visible rows to 12 at 1280x720. The collapsed strip and other pages are unchanged.
• Details in ConversationRail:
  • The list no longer has its own scroller. The held header gets a solid backing and an edge only while it is held, and a data-stuck attribute written straight to the DOM, so no re-render.
  • Paging and the held-header observer now use the rail region as their root, so the 120px look-ahead works again.
  • The section keeps the region's height while a search narrows the list, so the search box doesn't jump.
  • Keyboard focus on a row under the held search is moved clear of it (WCAG 2.4.11). This is a small :focus-visible handler, because Chromium ignored scroll-margin here and scroll-padding threw the list 516px whenever the search box took focus.
• Workflow alerts pop from the bell instead of My Workspace, which the rail can now scroll away:
  • Expanded rail: the notice drops below the bell like the bell's panel does, hanging past the rail edge.
  • Collapsed rail or phone: it flies out beside the bell.
  • It follows the bell in the tab order.
• Merged with V2 workflow alerts: require acknowledgment, repeating sound, size options and team delivery (0.261.235) #1636 (must-acknowledge alerts). V2 workflow alerts: require acknowledgment, repeating sound, size options and team delivery (0.261.235) #1636 gave those alerts their own room below My Workspace so they never cover anything. That room is now WorkflowAlertRowSlot, a row under the rail header. Its notch is measured to point at the bell, it pushes New chat and the nav down, and it sits outside the scroll region. The flyout keeps V2 workflow alerts: require acknowledgment, repeating sound, size options and team delivery (0.261.235) #1636's step-aside. This PR is renumbered to 0.261.236, since V2 workflow alerts: require acknowledgment, repeating sound, size options and team delivery (0.261.235) #1636 took 0.261.235.

Before: at rest (list squeezed to 2 rows)	After: list scrolled, search held under New chat

Ordinary alert: drops from the bell	Needs acknowledgment: its own row under the bell

Linked issue

Fixes #1642

Refs #1636 (must-acknowledge alerts, reconciled in the merge commit), #1553

Release Notes & Latest Features

• New Feature
• Bug Fix
• UI Enhancement
• Breaking Change
• Internal only

Is this visible to end users?

• Yes
• No

Is this admin-facing (Admin Settings, governance, deployment, config)?

• Yes
• No

Should this become a Latest Feature card?

• Yes
• No
• Already added

Screenshot needed for the card?

• Yes
• No
• Attached

Version bump

• application/single_app/config.py VERSION third segment bumped, or not needed because this is docs-only (0.261.235 -> 0.261.236)
• deployers/version.txt bumped, or not needed because deployers/ was not changed

Testing / validation

All run on the merged branch (after #1636), with the V2 bundle rebuilt:

• npm --prefix application/v2_ui run typecheck: passed
• python functional_tests/test_v2_sidebar_conversation_scroll.py: 8/8 passed
• python -m pytest ui_tests/test_v2_workflow_alert_notices.py: 60 passed (includes V2 workflow alerts: require acknowledgment, repeating sound, size options and team delivery (0.261.235) #1636's must-acknowledge tests and the new bell/row geometry checks)
• python -m pytest ui_tests/test_v2_sidebar_conversation_scroll.py ui_tests/test_v2_notifications_bell.py ui_tests/test_v2_new_chat_reset.py ui_tests/test_v2_workflow_alerts.py: 90 passed
• python -m pytest <file>, one file at a time: all passed for test_v2_new_chat_scoping (6), test_v2_sidebar_account_menu (8), test_v2_conversation_multiselect (17), test_v2_notifications_bell (10), test_v2_brand_mark_home_link (4), test_v2_conversation_drawer (8), test_v2_conversation_export (15), test_v2_shared_conversations (14), test_v2_inline_image_proposal_resume (10), test_v2_settings_and_workspace_tags (9), test_v2_api_payload_shapes (6), test_v2_public_workspace_labels_pin (2), test_docs_site_quality (6), test_docs_app_surface_coverage (7), test_v2_alert_lab_excluded_from_build (4), test_workflow_alert_acknowledgment (53), test_workflow_alert_client_parity (100), test_workflow_alert_bounded_query (48), test_workflow_alert_error_redaction (25), test_workflow_alert_sounds_setting (6), test_workflow_alert_sound_parity (3), test_workflow_alert_sound_assets (2)
• Visual pass: the screenshots above come from the real AppShell with production CSS (stubbed HTTP). The notch-to-bell offset measures under 1px in every placement.

Pre-existing failures, identical on the base tip 5be1d84 (not touched by this PR)

This PR's only backend change is the VERSION string. Each of these gives the same result when run against an extract of the base tip in this environment:

• test_v2_conversation_deep_link::test_incoming_link_is_captured_before_any_effect_runs and test_v2_stats_parity::test_charts_use_the_shared_vendored_runtime: the asserted code isn't in the base's ChatPage.tsx / InlineChart.tsx, neither of which this PR changes.
• test_workflow_alert_notifications_import_cycle: the 2 scheduler-runner-first cold-import variants fail.
• test_workflow_priority_alerts: 2 fail.
• test_workflow_alert_since_hours_policy: 1 failure plus setup errors.
• test_workflow_alert_acknowledge_policy and test_group_workflow_file_sync_client_parity: fixture setup errors.

Documentation

• Release notes updated, or not needed (new v0.261.236 section)
• Feature documentation updated, or not needed (REACT_V2_UI.md, V2_WORKFLOW_ALERT_NOTICES.md, WORKFLOW_ALERT_ACKNOWLEDGMENT.md, guides/manage-notifications.md, reference/chat-controls.md)
• Fix documentation updated, or not needed (new fixes/V2_SIDEBAR_CONVERSATION_SCROLL_FIX.md)

Security checklist

• New Flask routes include @swagger_route(security=get_auth_security()) (no routes added)
• Settings sent to non-admin frontends use sanitize_settings_for_user() (no settings payloads changed)
• Browser JavaScript is served from local SimpleChat static assets only; no CDN-hosted JS
• No secrets, keys, connection strings, or local-only artifacts are included