fix(commands): construct complete synthetic key events

[nightcityblade]

Problem and impact

Synthetic command events were partial objects asserted as KeyEvent. Matchers or programmatic handlers that inspected required event metadata or propagation state could observe missing or inert behavior.

Approach

Construct OpenTUI's exported KeyEvent with the existing chord fields plus explicit press / raw synthetic defaults. This keeps chord matching unchanged while using OpenTUI's real prevention and propagation state. No command-dispatch or public extension API behavior is otherwise changed.

This belongs in the existing core command-key helper because it owns synthetic events used by conflict detection and command invocation.

Verification

• bun test src/lib/commandKeys.test.ts (3 passed)
• bunx oxfmt --check src/lib/commandKeys.ts src/lib/commandKeys.test.ts .changeset/complete-synthetic-key-events.md
• bunx oxlint src/lib/commandKeys.ts src/lib/commandKeys.test.ts --deny-warnings
• bun run typecheck

Tested on macOS. No visual evidence is applicable because this changes the internal event contract without altering rendering.

Fixes #767

[greptile-apps]

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