v0.9.0 - Public API audit and hardening

Eight findings from a full public-API audit of v0.8.0 - a symbol-by-symbol
inventory, then a phased pass over naming, signatures, exceptions,
mutability, subclassing contracts, documentation, concurrency posture, and
import surface. All eight accepted, none rejected. Same methodology as
always: nothing taken from a summary, every finding reproduced against the
actual source before deciding on a fix.

🔒 Added

• SETTOrchestrator.verify_ethical_audit_log(): delegates to
  EthicalFilter.verify_audit_log(), reachable from the orchestrator
  itself instead of requiring access to the private _ethical_filter
  attribute. Closes a real gap: v0.8.0's tamper-evidence guarantee was
  invisible to anyone using only the documented entry point.
• SETTValidationError(SETTError, ValueError): deliberate multiple
  inheritance, the same pattern the standard library's own
  json.JSONDecodeError uses. RiskProfile.__post_init__ now raises this
  instead of a plain ValueError; both except SETTError and
  except ValueError still catch it.
• A non-blocking warning (logged, not raised) when a PhrasingExpert
  subclass overrides resolve() against its own documented "template
  method, do not override" contract. Fires at instantiation, does not
  prevent the override from working.

🐛 Fixed

• PrivateMemory.read() and get_all() returned mutable references into
  internal state: a caller mutating a nested value could corrupt stored
  data without ever calling write(), with no trace in get_history().
  Both now return deepcopy()s, the same treatment UniversalMemory
  already received in v0.8.0.
• tests/test_elevenlabs_adapter.py now guards with
  pytest.importorskip("requests"). Previously, a bare install (pip install -e ., without the [elevenlabs] extra) made these 12 tests
  FAIL instead of skip, contradicting the project's own documented
  install instructions. Present unchanged since v0.8.0 as published.

🗑️ Removed

• sett/services_gen_ai/: an empty scaffold module (a one-line docstring,
  no classes, no functions, not referenced anywhere) since v0.1.0. Will be
  recreated with real content if a concrete use case appears.

📝 Docs

• api_reference.md: documented SafetyAssessment, ContextAnalysis,
  TTSBase, STTBase, SentimentBase, SentimentResult, and
  SentenceSentiment - all public, exported, used in real tests,
  previously undocumented. Added a field table for EthicalRule.
  Documented EthicalFilter.verify_audit_log() /
  SETTOrchestrator.verify_ethical_audit_log(), and added sequence,
  previous_hash, and entry_hash to the audit log field lists. Added an
  explicit Concurrency section: no thread-safety guarantee for the
  framework as a whole beyond UniversalMemory's internal lock.

✅ Compatibility

Low risk, but not zero: import sett.services_gen_ai now raises
ModuleNotFoundError instead of importing an empty module. RiskProfile
now raises SETTValidationError instead of a plain ValueError; existing
except ValueError handlers keep working unchanged, since
SETTValidationError is one. No other public signature changed.

Status

• 275 tests passing (264 before this round), 11 new.
• Full audit methodology and findings: see CHANGELOG.md.