v0.13.1 - Fail-closed routing preflight and benchmark-driven overhead fix

A frozen comparative benchmark exposed avoidable steady-state action
latency in SETT's governed execution path. Follow-up scenario-level
profiling and repeated ablation isolated two confirmed contributors:
synchronous logging.lastResort writes when the host application had
not configured logging, and governance work performed before handler
availability was known.

This patch fixes both causes while preserving fail-closed execution,
boundary integrity, sanitized trace completeness, and compatibility
with v0.13.0.

🔄 Changed

• Importing sett now installs a package-level
  logging.NullHandler without configuring the root logger.
  Applications that never configured logging no longer fall through to
  Python's synchronous stderr lastResort handler. Handlers installed
  by the application continue receiving propagated records normally.

• SETTExecutor.submit() resolves the exact handler before copying
  payloads, reading environmental context, or invoking the
  EthicalFilter. An unroutable action emits action.blocked with
  verdict block and reason handler.not_registered, then raises a
  structured SETTConfigurationError. It does not manufacture an
  ethical verdict or handler failure for something that never had a
  route.

• SETTExecutor.submit_controlled() performs the same readiness and
  route preflight before payload snapshots, fingerprints, idempotency
  reservations, or handler-attempt events. An impossible action cannot
  consume an idempotency key or fabricate an attempt that never reached
  a handler.

🐛 Fixed

• The concurrency reference now counts and names its five narrow
  thread-safe exceptions consistently, including UniversalMemory in
  the practical deployment guidance.

• CartesiaTTSAdapter now reports a blank voice_id as a structured
  SETTServiceAdapterError with configuration metadata instead of
  leaking a native ValueError.

• The v0.13.0 changelog entry now includes release-audit changes that
  were present in the published v0.13.0 source and release notes but
  were mistakenly carried into the draft v0.13.1 entry. This corrects
  the historical record and does not attribute those changes to this
  patch.

• README.md's Install section documented pip install sett-framework
  as though the package were available on PyPI. It is not, and there is
  no near-term plan to publish it. The section, and
  docs/getting_started.md, now document installing from source.

Performance interpretation

Under the frozen SGBS-01 benchmark protocol, the repeated Stage 13
ablation measured, against the Stage 12 official run (three independent
repetitions each, run-to-run spread under 0.5%):

• Mean latency: 14.2% lower
• p95 latency: 23.8% lower
• p99 latency: 25.5% lower
• Throughput: 18.8% higher

These are observations under that protocol, not universal performance
guarantees.

The logging change affects emitted WARNING and ERROR records. The
routing change affects unroutable and unready actions. Neither removes
work from a registered ALLOW path.

The same ablation observed an approximately 7% improvement on registered
ALLOW-shaped paths. Those paths should not invoke either corrected
behavior, so that result remains unexplained and is excluded from the
patch's claimed effects pending isolated investigation.

The complete protocol, comparisons, and measurements will be published
separately as a citable benchmark report (SGBS-01).

✅ Compatibility

• Zero breaking changes. No public symbol was renamed, removed, or had
  its contract narrowed.
• All 995 tests inherited from v0.13.0 pass unmodified.
• The complete v0.13.1 suite passes with 1,003 tests.
• The private companion-assistant application's suite of 1,175 tests
  passes with zero application code changes.
• Zero mandatory dependencies were added.

💖 Sponsors

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

See the complete itemized history in
CHANGELOG.md.