Improve first-run onboarding

[drakulavich]

Summary

• add AGENTS.md that directs agents to the existing repository guidance
• hide interactive Personal Access Token entry and provide a safe non-TTY recovery path
• replace an empty first-run report with a clear sync instruction

Why

New users could accidentally expose their token during login or mistake an all-empty report for a broken CLI.

Relates to #28.

Validation

• bun test
• bun run build
• pseudo-TTY check confirming an interactive test token is saved without appearing in terminal output

[greptile-apps]

Greptile Summary

Improves first-run onboarding and maintenance coverage.

• Hides interactively entered Personal Access Tokens and provides non-TTY recovery guidance.
• Shows sync instructions when reports contain no available data while preserving sleep-detail-only reports.
• Updates CI artifact handling, dependency resolution, version assertions, documentation, and repository guidance.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains.

Important Files Changed

Filename	Overview
src/commands/login.ts	Adds hidden terminal token entry, cancellation handling, non-TTY guidance, and structured CLI error handling.
src/format-report.ts	Detects genuinely empty reports while preserving rendering when sleep details are available.
src/format-report.test.ts	Covers both first-run sync guidance and the previously reported sleep-detail-only report case.
.github/workflows/ci.yml	Skips JUnit conversion when the test report was not generated.
src/index.ts	Updates the exposed CLI version to 0.4.5.

_{Reviews (3): Last reviewed commit: "fix: synchronize Bun lockfile in CI" | Re-trigger Greptile}