feat(composer): drafts survive restart, ↑ recall, Enter-to-send option, batched review comments (#1493 B) - #1496

Item B of #1493.

What changed

1. Drafts survive a restart. Text, attachments (stored as paths, never image data), paste cards and review chips are saved per thread to localStorage, debounced and also flushed on unload, then restored on launch and cleared on send.
   • One storage key, capped at 1 MB in total. Over the cap, the largest paste cards are dropped first, then the ↑ history; text and attachments are always kept.
   • Drafts of deleted threads are pruned on idle.
2. ↑ recall. ↑ in an empty composer recalls the last prompt sent on this thread; ↑/↓ step through the last 20 while the recalled text is unedited. The slash and mention popups keep their arrows, and a non-empty draft is left alone.
3. Send-key setting. Settings › General › Display gets "Send with Enter (⇧ Enter for a new line)". It's opt-in: today's default (Enter = new line, ⌘/Ctrl+Enter = send) is unchanged. The keyboard sheet follows the setting and lists ↑ recall.
4. Batched review comments. A gutter comment in Changes no longer starts a run. It becomes a draft chip (src/a.ts:L12-18 comment) that can be edited or removed. ⇧-click extends a comment to a range within one hunk. All chips go out with the typed text as one prompt.

Verified independently

• Merges cleanly with main and with fix(threads): replay the thread's tail after a provider switch or dropped session (#1493 A, #237) #1494 and feat: native context compaction for Claude and Codex (#1493 E, #318) #1495. On main with all three merged: typecheck exits 0 and vite build passes.
• test:renderer: 2774 passed, plus 1 file cancelled under load (appWiring) that passes when re-run alone.
• Screenshots (range, chips, after reload, settings) reviewed: the chips sit above the typed text, and the range highlight and "Add to prompt" match the calm UI.

🤖 Generated with Claude Code