[smith-xyz]

Plan: 17-shaun-traust-core-only.md (part)

Deletes the metrics journal and model registry from the engine. Merge after traust-security/traust#294, which retires metrics history / metrics spend and moves registry models spend onto traust-core's SpendService.record. That PR also freezes traust's parity tests, which used registry/models.py and metrics/{collect,attribute}_spend as oracles, so nothing in traust imports what this PR deletes.

What

• Deleted src/traust_engine/metrics/ (history, spend, collect_spend, attribute_spend, ops) and src/traust_engine/registry/ (models, ops), along with the facade's .metrics and .models.
• Nothing else needed them (git grep -nE "traust_engine\.(metrics|registry)|MetricsOps|ModelsOps|\.models\(|h\.metrics" -- src tests is empty). ops/ uses core's SpendService and the model registry through core. portfolio/ never referenced them. In sweep/, benchmark.py's scorecard ran python -m traust_engine.metrics.history append as a subprocess. That was already a no-op, because history.py has no __main__ (test_no_cli_entrypoints). The call and its docstring line are gone.
• locations.METRICS_HISTORY_REL / metrics_history() (only metrics/ops.py used them) are deleted. The PENDING lists in the module docstrings drop "metrics journal". README, CODEOWNERS and the ruff per-file ignore for history.py are updated to match.
• .ratchet.json shrinks: metrics/history.py (contracts 2), metrics/spend.py (1), registry/models.py (1) and registry/ops.py (1) are removed.

Deleted tests

Test	Why
tests/test_metrics_history.py	the hash-chained journal is retired
tests/test_build_spend_dashboard.py	the legacy spend dashboard is retired
tests/test_attribute_session_spend.py	transcript attribution lives in traust-core (SpendService.usage_summary / attribute_by); traust's frozen parity tests keep the engine's output
tests/test_model_pricing.py	engine cost_usd / long-prompt pricing is deleted; core ModelCatalog.cost owns pricing
tests/test_model_registry.py	engine resolve/stamp/validate/spend_row are deleted; core ModelCatalog owns them, and traust's test_registry_doors keeps the engine's outputs
tests/test_traust_engine.py::test_metrics_journal_follows_configured_progress_tracker, ::test_metrics_spend_build_uses_configured_paths, ::test_models_registry_and_validate_from_context	test .metrics / .models, which are deleted

Changed tests

Test	Old → new	Why
tests/test_traust_engine.py::test_two_engines_are_isolated_by_their_context	isolation shown by h1.metrics.append rows → each engine's sweep._progress_tracker() follows its own context	.metrics is deleted; the property (one context per engine) is unchanged
tests/test_traust_engine.py::test_namespace_ops_are_cached_per_engine	drops the .metrics / .models lines	those namespaces are deleted

• A person reviewed each changed test and the behaviour change is intended

Behaviour changes

• HarnessEngine.metrics and HarnessEngine.models no longer exist (traust#294 removed the last callers).
• sweep benchmark score no longer starts a subprocess that did nothing. Output and exit codes are unchanged.

Validation

• make lint-fix && make test: 451 passed, 4 skipped (tree-sitter not installed), 5 subtests passed.
• Importing every module (pkgutil.walk_packages) works.
• Consumer ratchet as CI runs it (RATCHET pin from ci.yml, --reference = development's .ratchet.json in a file): rc 0 after the shrink (it asked for exactly these four).
• traust#294's suite with this branch installed in place of the pinned engine: 2657 passed, 2 skipped.

What traust still uses from the engine

load_engine → HarnessEngine with .sweep (sweep stages), .portfolio (portfolio graph) and .adapters (the rule lane's opengrep config). Tests also use locations, sweep.engine, sweep.benchmark and adapters.opengrep. All of these wait on PENDING(decision: sweep stages | portfolio graph layers).

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