Release v1.6.0

What changed

• Added execution provenance metadata to normalized JSON output:
  • metadata.model
  • metadata.execution_context
  • metadata.execution_context.runtime
• Added reproducibility context fields in execution_context:
  • provider_protocol
  • api_endpoint
  • model_requested
  • model_resolved
  • runner_version
  • prompt_hash (sha256:)
  • runtime snapshot (stream, system_prompt_provided, runtime controls, timeout, retries)
• Extended provider contract with resolved-model metadata hook (get_last_model_resolved) and
  integrated it across protocol providers.
• Extended output schema and runtime validators for new additive provenance fields.
• Expanded unit/schema coverage for provenance serialization, validation, and runner guard/error
  paths.
• Updated technical documentation to reflect v1.6 provenance behavior:
  • README.md
  • docs/cli-reference.md
  • docs/architecture.md
  • docs/configuration.md
  • docs/output-contract.md

Why it matters

• Improves traceability and auditability of each execution without changing the stateless
  architecture.
• Makes runs more reproducible by recording effective execution context (protocol, endpoint,
  requested/resolved model, runner version, runtime settings, prompt hash).
• Preserves the stable output contract while extending metadata in a backward-compatible additive
  way.

Stability Statement

• v1.6.0 is a stable feature release on top of the v1.x baseline.
• No CLI interface breaking changes.
• No provider contract breaking changes.
• No output contract breaking changes (additive metadata only).

Scope Clarification

• The project remains a deterministic, stateless execution layer.
• No orchestration, no memory, no agents, no multi-turn workflow behavior.
• No conversation state was introduced in this release.

GitHub Pull Requests Included

• feat(v1.6): add execution provenance metadata contract by @damienSavoldelli in #26
• release(v1.6.0): prepare provenance metadata release by @damienSavoldelli in #27

Full Changelog: v1.5.0...v1.6.0