refactor(test): simplify keyboard input handling and extract type definitions

Remove reliance on key.name and key.sequence in favor of using input directly.
Extract TTY type definitions for clarity and add scoping constraints to prevent
variable shadowing. Update AGENTS.md documentation for accuracy.

AGENTS.md

@@ -15,19 +15,16 @@ Short guide for AI agents in this repo. Prefer progressive loading: start with t
 - `localdocs/` (optional deep dives)
 
 ## Shared rules
+- No backward compatibility: breaking old format freely.
 - TypeScript strict; no untyped code.
 - Bun workspaces; run `bun` commands from repo root.
 - Path alias `@/*` maps to `./src/*` per package.
-- No backward compatibility: breaking format changes are allowed.
 - Prefer 4-space indentation.
 
 ## Common commands (repo root)
-    bun run build
-    bun run build:single-exe
-    bun run typecheck
-    bun run dev:server
-    bun run dev:web
-    bun run test
+
+- `bun typecheck`
+- `bun run test`
 
 ## Key source dirs
 - `cli/src/api/`, `cli/src/claude/`, `cli/src/commands/`, `cli/src/codex/`