feat(update): add cached CLI update experience

[Hweinstock]

Problem

AgentCore only checks for updates when users run agentcore update, so users can remain on an old version without knowing it. This change adds cached npm version checks, a once-daily notice, and a TUI version/update flow while keeping passive checks non-fatal.

Solution

• Add CliVersionManager, implemented by NpmCliVersionManager, for active/latest versions, notices, and installation.
• Cache latestVersion and lastCheckedAt per npm dist-tag in ~/.agentcore/update/{dist-tag}.json.
• Put the version manager in routed context under CliVersionManagerKey; feedback, update commands, and the TUI use that single dependency.
• Run the passive notice check as a root-level best-effort lifecycle step alongside telemetry.
• Read the package version once at startup for logger and telemetry setup.
• Show current/latest versions in the TUI and require confirmation before installing.
• Log passive registry and cache failures while preserving command execution.

Verification

• bun test — 3,595 passed
• bun run typecheck
• bun run lint
• bun run format -- --check
• bun run build

Notes

• Passive checks occur at most once per 24-hour cache window.
• Explicit checks and installs perform live registry lookups.
• Updates install the exact version returned by npm.
• The registry request uses a two-second timeout.
• Manual screenshots and screen-recording evidence can be attached before moving the PR out of draft.

[Hweinstock]

TUI update evidence

Current version indicator

Available update and confirmation

The update screen is reached through normal TUI navigation: filter for update, press Enter, and stop at the confirmation prompt. No installation was confirmed or run.