SW-096 — Normalize CLI error-category wording

[dDevAhmed]

Summary

Align validation/subprocess/internal/unexpected error wording while preserving centralized exit-code categories.

Acceptance Criteria

• representative categories use consistent user-facing wording;
• stack traces/raw unexpected details remain hidden;
• exit codes do not change;
• repository checks pass.

Dependencies

• SW-007

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🏷 Labels

• Stellar Wave
• type: ux
• area: cli-core
• priority: P1
• difficulty: medium
• points: 150
• workstream: cli-core