fix(vscode): restore Agent Manager build within line cap

[marius-kilocode]

What Problem This Solves

The VS Code extension build on main fails because AgentManagerApp.tsx has 2,818 lines, above its 2,800-line ESLint limit.

Why This Change Was Made

Extract the keyboard shortcuts dialog into a focused component. Keep the existing line cap, shortcut data snapshot, translations, markup, and styling unchanged. Include the component in the CSS architecture checks.

User Impact

Restore extension builds without changing Agent Manager behavior. AgentManagerApp.tsx now has 2,792 lines. This is a build-only refactor, so no release changeset is needed.

Evidence

• Reproduced the max-lines error on current main.
• Full bun run compile passes, including CLI preparation, SDK preparation, host/webview typechecks, lint, and bundling.
• Unit suite: 4,721 passed, 1 skipped, 0 failed.
• Knip, kilocode-change guard, and touched-file formatting checks pass.
• Initial missing-dependency failures were resolved with a worktree-local frozen-lockfile install.
• No interactive VS Code smoke test was run. Manual check: open Agent Manager keyboard shortcuts, verify categories and key badges, then close and reopen the dialog.