[codex] Fix keyboard shortcut handling

[ctoth]

Summary

• Tighten Alt navigation handling so the app only consumes plain Alt navigation chords, not Alt plus extra modifiers.
• Add output review shortcuts: Ctrl+1 through Ctrl+0 now read the last 1 through 10 output lines.
• Move sidebar tab switching to Ctrl+Shift+1 through Ctrl+Shift+0.

Root Cause

The global channel-history handler and focused input/output suppressors treated some Alt chords too broadly. Separately, Ctrl+number was already reserved for sidebar tab switching, leaving no direct shortcut for reviewing recent output lines.

Validation

• npm test -- --run src/hooks/useChannelHistory.test.tsx src/components/input.test.tsx src/components/output.test.tsx src/App.test.tsx
• npm run typecheck
• git diff --check on touched files
• Precommit hooks ran during both commits; typecheck passed. Biome reported existing warnings in App.tsx and output.tsx, but did not block.