emrg: GUI session history on-demand loading (rant 2026-08-13T14:15:12 front-end)

[argszero]

Front-end of GUI session-history on-demand loading (host rant 2026-08-13T14:15:12); backend pagination landed in #737.

• emrg/gui/main.js emrg:listHistory: passes optional limit/offset through to the daemon, returns hasMore.
• emrg/gui/renderer/js/app.js: on non-silent switchSession loads the most recent 50 messages (read-only user bubbles, Chat.addHistoryMessage); per-session historyPages state (offset/hasMore/loading); scrolling the session view to the top loads an older page (prepend + scroll-position compensation, 150ms debounce); load bar shows ↑ 加载更早消息 → 没有更多历史.
• emrg/gui/renderer/js/chat.js: addHistoryMessage (read-only, prepend-aware) + setLoadBar (top bar element).
• emrg/gui/renderer/css/components.css: .msg.user.history (dimmed) + .history-load-bar styles.
• emrg/gui/renderer/js/i18n.js: zh/en keys app.historyLoadMore/historyLoading/historyNoMore.
• test/renderer.smoke.test.js: +1 smoke test (switch loads page 1 + load bar; scroll-to-top loads page 2 with offset=loaded; prepend keeps count). GUI 231→232 (renderer smoke 109→110); Agent.md synced.

/rewind list stays full-list (no limit passed) — no regression.

[argszero]

✅ LGTM — cycle (1/3)

Reviewed the GUI front-end for #737's backend pagination:

• main.js: optional limit/offset passed through to the daemon, has_more → hasMore — matches the list_history protocol from #737.
• app.js: per-session page state (offset/hasMore/loading), loadHistory on non-silent switch (50 newest), loadOlderHistory prepends with scroll-position compensation (delta scrollTop + (scrollHeight - prevHeight)), debounced scroll-to-top trigger (150ms, passive), load-bar states (load-more / no-more), error fallback to a system message.
• chat.js: addHistoryMessage reuses the user-bubble style + .history dimming; prepend anchors after the load bar (scroll position preserved); App.updateEmptyState?.() consistent with existing patterns.
• i18n zh/en both added; CSS dims history bubbles (visual distinction from live messages).
• Smoke test is discriminative: asserts limit=50/offset=0, 2 bubbles rendered, load bar shown, scroll→second call offset=已加载数, prepend → 3 bubbles, no-more state.
• Verified locally: cd emrg/gui && npm test → 232 pass / 0 fail; Agent.md GUI counts synced (231→232, 109→110 renderer smoke); CI test + test-windows PASS (31674780319).

Non-blocking nit: app.historyLoading i18n key is currently unused (no visible loading state while fetching) — fine to keep for a future spinner.

[argszero]

✅ LGTM — cycle. CI test + test-windows both pass (run 31674780319); 773 pytest + 232 GUI tests green locally (renderer smoke +1: switch loads page-1 history + load bar; scroll-to-top prepends page-2 with offset=loaded); emrg:listHistory passes limit/offset through; Agent.md GUI count synced 231→232.

[argszero]

✅ LGTM — cycle (3/3)

Re-verified against current master d855ef6: diff unchanged (f02982d), mergeStateStatus CLEAN, CI test + test-windows PASS (run 31674780319). GUI pagination front-end for #737 — per-session page state, scroll-to-top prepend with position compensation, read-only history bubbles, zh/en i18n, discriminative smoke test. Three consecutive ✅ from different cycles with no ❌ in between — merging.