feat(workspace): the scanline is for charts, and the conversation gets its rail (#2540, ent#474)

[trinity-ability]

Summary

Two operator rulings from the 2026-09-06 Workspace review, in one PR because the second is built under the first.

• refactor(ui): the scanline reveal is for chart loading only — take it off the Workspace stage, thread and briefing; pages and lists load with skeleton placeholders #2540 — the loading rule. Design-system principle 12 is amended: the scanline beam + wipe-in reveal is the chart-loading motion only; every other first load (pages, panels, lists, threads) is a skeleton placeholder keyed on "no data yet". The three Workspace zones perf(workspace): the roster's latency floor is its slowest agent — defer briefing hydration off the critical path #2163 wrapped in ScanlineReveal — stage, thread, briefing — now render PortalSkeleton, gated on stage.state === 'loading' / !historyLoaded / zone.state === 'pending' (never a bare <x>.loading path, which the bug: background polls re-flash loaded content and reset UI state (design-system p13/p14) #1927 ratchet counts). The ScanlineReveal importer set is pinned as an allowlist; the two pre-ruling non-chart holdovers (LibrarySkillsSection, FinishSetupCard) are recorded on refactor: replace bespoke spinners with skeleton placeholders on non-chart surfaces (scanline stays on charts only — design-system p12 as amended 2026-09-06) #1921, whose sweep is re-pointed to skeletons.
• ent#474 — the rail shell, to the approved design pass (48px collapsed / w-96 open, trinity-workspace-rail, mobile strip + sheet, two signal shapes). Scope is the operator's own split: the three-column layout, the tab contract, the collapsed signal, and Work docked empty — its content is bug: long strings in chat responses break layout in chat tab #457's; loops / canvas / files re-home in fix(security): operator-queue access control — scope items to accessible agents (#470) #472's second child; the sidebar, thread tab strip, top band, Agent-details panel and drop target of the approved conversation page are later steps of the same build; chore(#488): ship status-in-dev automation to main #492 lands the grid variables the rail's widths then follow.

How the rail works

• components/portal/portalRail.js is the contract: a tab declares its door (platform / audience / agent), participant scope, empty state and signal shape. visibleTabs is the one gate for render and mount — a tab whose door the session fails has no icon, no label and no mounted body, so nothing it would fetch is ever requested. An unknown door fails closed. Today an external client sees no rail (Work is platform-only); with the four-tab set they see Canvas · Files.
• PortalRail.vue is a sibling of <main>, outside convKey: a chat switch remounts the conversation, never the rail. Visibility keys on the route and the stage verdict, never on data still arriving. Collapsed by default; open/collapsed + active tab persist under one key, read before first paint.
• The Work signal is derived, never latched — from the conversation's in-flight sending (1:1) and the room's server-reported working list — reset on every chat switch and cleared on unmount.
• A room groups every tab by participant (portalLoopUtils.byAgent), absence visible; OverflowTabs gains an optional per-tab signal dot measured in its mirror row; the mobile strip sits above the composer through a #rail-strip slot on both conversations and opens the same component as a bottom sheet (Esc closes).

Changes

• New: portal/portalRail.js, portal/PortalRail.vue, portal/PortalRailStrip.vue, portal/PortalSkeleton.vue
• Edited: views/Portal.vue (stage skeleton, rail wiring), portal/PortalConversation.vue + portal/PortalRoom.vue (thread skeleton, #rail-strip slot, work-state / participants-changed emits), portal/PortalBriefing.vue, portal/portalBriefingState.js (the reveal verdict is gone), components/OverflowTabs.vue (additive signal)
• Docs: design-system.md §6 + principle 12 + §8 table, design-system-contract.md, requirements §5.16 (amended) + new §5.19, feature-flows/workspace-rail.md (new), workspace-roster-briefing.md, architecture/workspace.md, the flow index
• Tests: portalLoadingTreatment.spec.js (new), portalRail.spec.js (new), portalBriefingState.spec.js + workspaceRoomsGate.spec.js (updated for the skeleton gate)

Test Plan

• npm run test:unit — 1889/1889 across 86 files (both ratchets green: no bare loading gate added; no touched file's raw-gray count grew — measured against origin/dev)
• Live on the Docker frontend (Playwright): collapsed strip → open rail with the Work empty state → persisted across reload; light and dark; mobile (390px) strip above the composer → bottom sheet → Escape closes; the stage skeleton renders with aria-busy under a slowed roster; no console errors
• Reviewer: open a room — every participant gets a row with "nothing in flight"; the 1 running badge appears while an agent is working (rides the room's working list)

Fixes #2540
Part of abilityai/trinity-enterprise#474

🤖 Generated with Claude Code

https://claude.ai/code/session_01FgAncnTAbgjJS3EGwuEtd4

[vybe]

Validated via /validate-pr: security scans clean, unit suite 1889/1889 on the PR head in Docker, both ratchets flat, docs updated across requirements / architecture area file / feature flows. Structural spot-check of the door gate, derived signal and stage skeleton found no issues. Approving.