v0.12.0 - Execution lifecycle, idempotency, and the first public release

Cooperative cancellation, deadlines, structured outcomes and idempotency
for executions already in flight, together with the hardening this
release's own auditing turned up along the way - several of those
fixes correct behavior that had been wrong since well before v0.12.0.
This is also the first public release of SETT: everything here was
already built and versioned internally (0.1.0 through 0.12.0), and this
is the first version anyone outside the project can install or link to.

✨ Added

• Immutable lifecycle primitives in sett/core_ruler/lifecycle.py:
  ExecutionControl, ExecutionControlRegistry, CancellationToken,
  CancellationSource, CancellationSnapshot, Deadline. A control
  carries its own ExecutionContext; subtree cancellation walks the
  parent_id chain that context tree already maintains, so no second
  hierarchy is introduced.
• Cooperative cancellation with LIFO cleanup hooks, monotonic deadlines
  a nested unit can shorten but never extend, lifecycle_scope()
  propagation via contextvars, and LifecyclePolicy for per-level
  timeout defaults - run, stage, agent, adapter, handler.
• ExecutionStatus, ExecutionState, ExecutionResult: six terminal
  statuses that keep an ethical rejection, a cancellation, a deadline and
  a technical failure apart. unwrap() re-raises the original exception
  instance, preserving its concrete type.
• SETTOrchestrator.process_controlled() / run_pipeline_controlled() /
  cancel(run_id), added alongside the existing entry points the same way
  process_traced() was in v0.11.0.
• Idempotency in sett/core_ruler/idempotency.py: action_fingerprint(),
  the IdempotencyStore protocol, InMemoryIdempotencyStore, and the
  record/reservation/attempt types behind it.
• RetryPolicy, ErrorClass, classify_error(). Retries are opt-in
  per error type; a set of framework errors is never retried regardless
  of policy.
• SETTExecutor.submit_controlled(), register_controlled_handler(),
  and HandlerContext, carrying the idempotency key and the run's real
  remaining time into a handler.
• SETTCancelledError, SETTTimeoutError, SETTDependencyError,
  SETTIdempotencyConflictError, all under SETTError.
• Eleven new test modules.

🔒 Security

• Per-instance Google Cloud credentials: TTS, STT and sentiment adapters
  no longer set GOOGLE_APPLICATION_CREDENTIALS process-wide, where two
  differently configured instances used to interfere with each other and
  with every other Google client in the process.
• Sensitive metadata and trace keys were matched by plain substring, so
  apiKey, x-api-key, api.key and private/key all passed. Keys are
  now normalized to letters and digits before comparison.
• RiskProfile values could reach UniversalMemory through an
  uncooperative agent despite the documented boundary. The check is now
  structural, at the one place every publication passes through.

🐛 Fixed

• A non-finite risk_score from a ContextAnalyzer reached ALLOW -
  nan comparisons are always False in Python, so a fail-open slipped
  through the layer meant to fail closed.
• SETTExecutor.submit() and UniversalMemory.update() each read a
  caller-held object twice; a concurrent mutation between reads could let
  policy approve one payload while the handler performed another.
• PrivateMemory.get_history() returned live internal entries instead
  of copies.
• ElevenLabsTTSAdapter accepted a whitespace-only API key.
• Provider SDK exceptions escaped adapter constructors untranslated
  (OpenAI, Anthropic, Gemini, and Google client construction). Every
  construction failure now leaves as a SETT error, with the original
  preserved as __cause__.
• Adapter timeouts skipped the NaN/infinity validator this release
  otherwise applies everywhere.
• An invisible character (zero-width space, fullwidth spelling) was
  enough to dodge a ContextAnalyzer keyword match; text is canonicalized
  first now.
• OllamaAdapter let a malformed base_url escape as a bare
  ValueError instead of a SETTLLMAdapterError.
• HandlerContext.attempt_number reset to 1 on every resubmission of
  the same idempotency_key instead of climbing with it, the way
  IdempotencyRecord.attempt_count already did.

⚠️ Breaking changes

• EnvironmentalContext.auto_notify_emergency is now
  should_notify_emergency (attribute and to_dict() key).
• register_expert() / register_handler() /
  register_controlled_handler() / register_analyzer() now refuse a
  duplicate instead of silently replacing it. register_agent() still
  replaces - that is how a StubDomainAgent gives way to the real
  implementation - but now warns when what it replaced was not a stub.

🔄 Changed

• PrivateMemory.write() stores a deep copy; clear() now records an
  audit entry too.
• Timeouts and durations reject NaN and infinity everywhere, through
  one validate_duration_seconds().
• An Action carrying an idempotency_key must have a
  JSON-serializable payload.
• docs/api_reference.md now covers every name in sett.__all__, with
  attribute tables for the four new exceptions; the concurrency section
  names ExecutionControlRegistry and InMemoryIdempotencyStore. Every
  public definition carries a docstring. Three new guard tests keep all of
  this from drifting again.
• docs/SETT_Conventions_v2.md is now docs/SETT_Conventions.md - no
  version of SETT has been public before now, so no external reader ever
  had a reason to link the old name.

🗑️ Removed

• The per-version MIGRATION_v*.md mechanism. No version has shipped
  externally before now, so there is no adopter for a migration guide to
  serve; CHANGELOG.md is the record of what changed and why.
• The per-release AUDIT_vX.Y.Z.md file. Only AUDIT_v0.11.0.md was
  ever produced under that name; no version before it had one, and this
  release does not restart the pattern - a single instance was never a
  convention to begin with. CHANGELOG.md is the record of what was
  verified for a given release and why.

✅ Compatibility

• process(), run_pipeline() and submit() were deliberately not
  rewired to their controlled counterparts in this release.
• The 340 tests of v0.11.0 pass unmodified.

💖 Sponsors

• Sponsors: eight tiers from a symbolic $1 up to logo
  placement on 4humanityAI.com, with an explicit note on what sponsorship
  does and does not buy.

Known limitations

• SETT cannot cancel an arbitrary non-cooperative Python handler; three
  levels of guarantee are documented (cooperative code, a provider given
  the remaining time, untrusted code that belongs in an isolated process).
• Exactly-once is not offered against an external system; an in-memory
  idempotency store says nothing about anything before the current
  process started.
• Canonicalization does not defeat homoglyphs (Cyrillic а vs Latin
  a) - a hand-maintained confusables table would produce confidence
  rather than safety. What guards a critical action is SETTExecutor
  resolving handlers by exact action_type and failing closed, together
  with a domain-specific analyzer.
• The public namespace of the submodules (names without a leading
  underscore that live outside sett.__all__) has no formal policy yet;
  that decision belongs to the v1.0 freeze. Full list in CHANGELOG.md.

Status

• 893 tests passing (828 immediately before this release's hardening
  pass, 340 at v0.11.0).
• Reference-consumer compatibility: the private companion-assistant
  application's suite (1146 tests) passes against this source release
  without any application code changes, with exactly one expected failure
  (an intentional version-pin guard, unrelated to this release).
• Zero mandatory dependencies in the core framework - every provider
  integration (OpenAI, Anthropic, Gemini, Ollama, Google Cloud,
  ElevenLabs) is an optional extra.

See CHANGELOG.md for the complete, itemized history of this and every prior internal version.