fix(config): format message-tone error with clean comma-separated list (#717)

[harmehak0173]

Slice

• Repo: doberman-core
• Feature / Slice: config: the message-tone error prints a Python tuple #717 - message-tone error formats Python tuple
• Plan reference: n/a (issue-driven bug fix)

What this PR does

Fixes the error message when an invalid message tone is configured. Previously, MESSAGE_TONES was formatted directly into the f-string, printing a raw Python tuple representation (('human', 'technical')). It is now formatted as a clean, human-readable comma-separated string (choose one of: human, technical).

Tests added (run in CI)

• Updated tests/unit/test_message_tone.py:
  • test_save_rejects_an_unknown_tone: verifies exact error message pattern and confirms raw tuple formatting (' is absent.
  • test_cli_rejects_an_invalid_tone: verifies CLI error output and confirms raw tuple formatting (' is absent.

Changelog

• changelog.d/724.fixed.md fragment added

Public-release safety (doberman-core only)

• Contains nothing from the "not allowed" list: no enterprise/hosted code, no proprietary detection, no customer data, no secrets, no commercial-license code
• Core still builds/tests/runs with NO enterprise package installed

Security checklist

• Fails closed on error / uncertainty
• No secret, full file, or unredacted prompt logged or committed
• Any guardrail/learning change is raise-only (no silent loosening)
• Every BLOCK/AUTH carries reason codes + a human explanation
• doberman-core does not import doberman_enterprise

Edge cases covered / Deviations from plan / Risks introduced

None.

Fixes #717