emrg: gui renderer Batch 2 remainder — Composer + CommandMenu + history pagination

[argszero]

GUI renderer Batch 2 remainder — Composer + CommandMenu + history pagination

Continues the React migration (design ~/.emrg/designs/gui-react-migration-design.md, Batch 2 remainder deferred from #994 until #990/#995 merged — the Agent.md doc-count line contention cleared).

Pure logic (new, zero-DOM, fully unit-tested)

• src/lib/history.ts — history on-demand pagination state machine (mirrors vanilla app.jshistoryPages, rant 14:15:12): HISTORY_PAGE=50, per-session {offset, hasMore, loading}, applyHistoryPage (empty page closes hasMore), scrollCompensation (visual-position-preserving pure function), shouldLoadOlder (≤2px + hasMore + !loading guard).
• src/lib/composer.ts — CommandMenu state machine (menuForPrefix / menuNavigate wrap-around) + P2 queue-injection send queue (emrg: queue messages sent while tool loop busy — inject at round boundary (P1, rant 2026-08-10T21:55:37) #655): queueSend / steerCommitted / partitionRequeue / trackAfterResend (wasBusy||i>0 re-tracking, the emrg: TUI queue-injection client support (P3 of #655) #695 lesson) / clearQueued — protocol-aligned with task_queued / steer_committed / queued_requeue / queued_cancelled.
• src/lib/transcript.ts — added prependHistoryMessage (older-page history prepends at top; loadBar stays a separate field above entries).

Component

• src/components/Composer.tsx — textarea (auto-grow ≤150px) + send button + / command menu with ↑↓/Enter/Esc keyboard nav and mousedown-select (preventDefault keeps focus), matching vanilla app.js keydown handler. Send flow: parseInput → command routing via onCommand callback (Batch 5 wires dialogs) / message → pre-generated requestId (G143), busy queue-injection (wasBusy), error restores input text + system message (G49, copy.sendFailed). sendMessage is injectable (defaults to window.emrg.sendMessage); busy is an optional controlled prop for Batch 5 daemon-broadcast wiring. CSS class names identical to vanilla (cmd-menu / cmd-menu-item / selected / composer-card / send-btn) for Batch 5 reuse.

Verification

• Renderer: npm run typecheck ✓, npm test129 passed (was 78; +15 history +22 composer +14 Composer), npm run build ✓
• GUI: npm test 265 (257 pass / 8 skip) ✓
• Python: pytest 1095 passed / 1 skipped ✓ (doc-count guard 4/4 — Agent.md renderer count updated 78→129)
• import + CLI checks ✓

External contracts untouched: window.emrg bridge, daemon protocol, Electron main/preload — zero changes.

[argszero]

✅ LGTM — cycle 20260826-171816

Reviewed resolved head 8844b9f (master merge 67d5508 + Agent.md conflict resolution: python 1099 from master + renderer 129 vitest; doc-count guard arithmetic exact — verified tests/test_doc_counts.py 4/4 locally).

Fresh review of the diff vs master (954 insertions, 8 files):

• lib/history.ts — pagination state machine mirroring vanilla historyPages (rant 14:15:12): HISTORY_PAGE=50, per-session {offset,hasMore,loading}, empty-page closes hasMore, scrollCompensation pure fn with Math.max clamp, shouldLoadOlder (≤2px + hasMore + !loading). 15 tests cover wrap/accumulate/empty/guard cases.
• lib/composer.ts — CommandMenu state machine (menuForPrefix/immutable menuNavigate wrap-around) + P2 queue-injection protocol helpers (#655): queueSend/steerCommitted/partitionRequeue/trackAfterResend (wasBusy||i>0 re-tracking, the #695 lesson)/clearQueued — protocol-aligned with task_queued/steer_committed/queued_requeue/queued_cancelled. 22 tests.
• components/Composer.tsx — textarea auto-grow ≤150px, cmd-menu ↑↓/Enter/Esc + mousedown preventDefault, send flow: parseInput → onCommand routing / message → pre-generated requestId (G143), busy queue-injection, error restores text + copy.sendFailed (G49). sendMessage injectable, busy optional controlled prop for Batch 5. CSS class names identical to vanilla for Batch 5 reuse.
• lib/transcript.ts — +prependHistoryMessage (older-page prepend; loadBar separate field).

Verification: renderer typecheck ✓, vitest 129/129 ✓, build ✓; gui npm test 265 (257+8) ✓; pytest 1095 passed/1 skipped ✓; import + CLI ✓. CI double-green on exact head (run 32952392415: test + test-windows pass); MERGEABLE.

External contracts untouched (window.emrg bridge, daemon protocol, Electron main/preload).

1/3.

[argszero]

✅ LGTM — cycle 20260826-172822

Re-verified on unchanged head 8844b9f:

• Diff vs master unchanged since cycle 171816 review (8 files, +954/−1: lib/history.ts, lib/composer.ts, lib/transcript.ts prependHistoryMessage, components/Composer.tsx).
• Agent.md python 1099 + renderer 129 vitest (post-conflict-resolution state); doc-count guard satisfied.
• CI double-green on exact head (run 32952392415: test + test-windows pass); mergeStateStatus CLEAN.

Consecutive with cycle 171816 (1/3), no ❌ between.

2/3.

[argszero]

✅ LGTM — cycle 20260826-173600

Third consecutive approval. Re-verified on unchanged head 8844b9f:

• Diff vs master: 8 files +954/-1 (lib/history.ts pagination state machine, lib/composer.ts CommandMenu + P2 queue protocol, transcript.prependHistoryMessage, components/Composer.tsx, +51 tests)
• Renderer suite on PR head: 129/129 vitest pass (13 files), typecheck OK, npm run build OK
• Doc-count guard 4/4 (Agent.md: python 1099 + renderer 129)
• CI double-green: test + test-windows (run 32952392415)
• Mergeable: CLEAN

Ready to merge.