Align CLI output with design guide

[Adjanour]

Summary

Refactor existing command output so every user-visible message matches docs/cli_design_guide.md for tone, density, and formatting.

Motivation

• Current outputs still include emojis and verbose text called out as anti-patterns.
• Consistent formatting reduces user friction and aligns with the documented philosophy.

Scope

• Update sess start, sess status, sess pause, sess resume, and sess projects to match the prescribed patterns.
• Ensure timestamps are relative when recent and durations use compact notation.
• Remove encouragement language and redundant headers.
• Add regression coverage where practical to guard formatting.

Out of Scope

• New command implementations (handled in other issues).
• Internationalization.

Acceptance Criteria

• Spot checks confirm outputs conform to docs/cli_design_guide.md examples.
• No emojis, heavy borders, or verbose duration strings remain.
• Tests or golden snapshots cover at least one command to prevent regressions.

References

• docs/cli_design_guide.md
• README.md (Design Principles)