emrg: GUI per-session chat-view containers — P3 slice 2 (GUI multi-session rant P3)

[argszero]

Summary

P3 slice 2 of the GUI multi-session rant (2026-08-10T15:07:19): per-session chat-view containers with display switching, building on P3 slice 0 (#630, per-session chat state isolation) and P3 slice 1 (#632, sessionsBySid state table).

Each open session now gets its own .session-view container under the #chat-view wrapper. Switching sessions toggles display (browser-tab effect) — scroll position, draft state, tool cards, and in-flight stream are fully preserved.

Changes

renderer/chat.js — chatContainer(sid) fallback chain: registered container → active session's container (unsid'd events land in the active session, P4 transition) → legacy #chat-view.

renderer/app.js

• ensureSessionView(sid) / activateSessionView(sid): get-or-create .session-view under #chat-view, toggle .active (only the active view is display:flex), register container (idempotent). Exported for tests.
• switchSession / newSession: activate the session view instead of Chat.clear() — switching away no longer destroys the other session's rendered state.
• deleteSession: unregister + remove the deleted session's container (if open).
• /clear and /rewind: Chat.clear(state.sessionId) — target the active session's container only.
• updateEmptyState: evaluate the active session's container (the wrapper always holds .session-view children, so counting the wrapper would break the welcome screen).

renderer/css/layout.css — #chat-view becomes a positioning wrapper (position:relative; overflow:hidden); .session-view = absolute inset:0 scroll container, display:none unless .active. Excluded .session-view from the legacy #chat-view > * centering rule so the scroll container stays full-width (scrollbar at window edge); media-query padding moved to .session-view.

test/renderer.smoke.test.js — +3 tests (container creation + display switching + unsid'd-node routing; targeted Chat.clear isolation; unregistered-sid fallback with per-sid state buckets). Test mock: innerHTML setter now faithfully clears children on "" (Chat.clear depends on it).

Verification

• GUI: 153 tests pass (43 daemon_client + 17 conn-manager + 22 app-commands + 43 renderer smoke + 15 i18n + 7 integration + 3 commands + 3 build-config); README/README.cn/Agent.md counts synced
• Python: 680 pytest pass
• node --check clean on all touched JS

Part of the staged P3 plan (remaining: P3 finalize/event-routing cleanup, then P4 open-sessions sidebar).

[argszero]

✅ LGTM — cycle 20260810-172123 (author). P3 slice 2: per-session .session-view containers with display switching; 153 GUI + 680 pytest green.

[argszero]

✅ LGTM — cycle 20260810-173337

Verified locally on the PR head: GUI suite 153/153 (43 renderer smoke — activateSessionView creates distinct per-session .session-view containers under #chat-view and toggles .active (only the active view display:flex); unsid'd nodes route to the active session's container (fallback chain registered → active → legacy); Chat.clear targets only the active container (inactive view retained — switch-back shows original messages); targeted clear(sid); unregistered-sid events render into active view while state buckets stay keyed by own sid; test mock innerHTML setter now faithfully clears children), 680 pytest green, doc-count guard passes (153 = 43 dc + 17 cm + 43 renderer smoke + 22 + 15 + 7 + 3 + 3 synced in Agent.md/README/README.cn), node --check clean.

Code review: #chat-view becomes a positioning wrapper with .session-view absolute inset:0 scroll containers (display:none unless .active) — browser-tab effect preserves scroll/draft/tool cards/in-flight stream across switches; switchSession/newSession activate instead of Chat.clear(); deleteSession unregisters + removes the container; /clear and /rewind target the active session's container; updateEmptyState correctly counts the active view (not the wrapper). Exported activateSessionView for tests. Builds cleanly on #630/#632; matches the rant P3 plan (remaining: P3 finalize/event-routing cleanup, P4 open-sessions sidebar).

[argszero]

✅ LGTM — cycle 20260810-173604

Re-verified on head 8e573ec: GUI suite 153/153 (43 renderer smoke incl. new P3 s2 tests — per-session .session-view containers created/toggled under #chat-view, unsid'd events route to the active container, targeted clear(sid) isolation, unregistered-sid fallback with per-sid state buckets), 680 pytest green, CLI import OK, node --check clean. Doc-count guard synced (153 = 43+17+22+43+15+7+3+3).

[pm25coder]

Tested this PR end-to-end on Windows — P3 slice 2 (per-session chat-view containers) verified.