Release v1.8.0 — content-addressed object store, replay, revision-aware lineage

[ignaden]

Release 1.8.0. Rebased onto main (1.7.1 + add lint + bump uv lock); version single-sourced (pyproject + uv.lock), changelog updated.

Added

• Content-addressed object store (ponens objects) — sha256-keyed blob store; trace references large content by content_ref instead of inlining it (dedup + portable bundles). Stable layout (<dir>/sha256/<ab>/<rest>, $PONENS_OBJECTS_DIR). CLI: objects put | get | externalize | inline | gc | stat; bind --externalize moves inline blobs into the store; objects inline rehydrates a bundle.
• ponens trace replay — re-run a ReproductionBundle: materialize the content-addressed model from the store and re-execute via a pluggable engine adapter (ImandraX), flagging verdict divergence. Dry by default; --run executes the safe-allowlisted command and preflights the engine.
• Revision-aware lineage (supersedes/revision) — current_artifacts, superseded_ids, revision_chain (cycle-safe); trace validate warns on a dangling supersedes.

Changed

• normalize_trace surfaces failed/aborted attempts (CommandResult outcome/exit_code onto its action → policies distinguish attempted-and-failed from never-attempted) and resolves externalized content_ref blobs for policy eval.
• Residual payload preserves summary / property / counterexample (Trace Spec v1.8 §13).

Verification

• 398 tests pass; gallery catalog regenerated (build_index/build_reasoners, --check clean).