feat(ui): add Ctrl-D and Ctrl-U scrolling aliases

[benvinegar]

Summary

• add Ctrl-D and Ctrl-U as default aliases for half-page scrolling
• preserve the existing plain d and u shortcuts
• cover the aliases in command and PTY tests and document the defaults

Closes #838

Testing

• bun run typecheck
• bun test src/ui/lib/appCommands.test.ts src/ui/lib/helpContent.test.ts
• bun test test/pty/pager.test.ts
• bun run lint
• bun run check:docs
• changed-file formatting check

This PR description was generated by Pi using gpt-5.6-sol

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
hunk-web	Ignored		Aug 26, 2026 12:01am

[greptile-apps]

Greptile Summary

This PR adds Ctrl-D and Ctrl-U as default aliases for half-page scrolling while retaining the existing plain d and u bindings.

• Updates the built-in command catalog and keybinding documentation.
• Adds command-level coverage for both aliases and their default-key declarations.
• Updates the PTY pager test to exercise the new control-key bindings in a live terminal flow.
• Adds a patch changeset for the user-facing behavior.

Confidence Score: 5/5

The PR appears safe to merge, with the new aliases aligned across runtime configuration, documentation, unit tests, and live PTY coverage.

The command matcher supports both named control-key events and bare terminal control bytes, higher-priority focused inputs and modes retain ownership, and no concrete conflicting built-in binding or broken navigation path remains.

Important Files Changed

Filename	Overview
src/core/run/commandCatalog.ts	Adds Ctrl-D and Ctrl-U to the existing half-page navigation commands without changing their semantics or removing prior bindings.
src/ui/lib/appCommands.test.ts	Verifies dispatch and catalog exposure for the new control-key aliases while preserving plain d/u coverage.
test/pty/pager.test.ts	Exercises both new aliases through the PTY-backed pager navigation flow.
docs/keybindings.md	Keeps the documented default-key table aligned with the runtime command catalog.

_{Reviews (1): Last reviewed commit: "feat(ui): add Ctrl-D and Ctrl-U scrollin..." | Re-trigger Greptile}