test: phase 0 conformance harness — typed parser for all 68 fixtures (#7)

Phase 0 of the v0.4 → v0.8 implementation plan: the conformance test
harness loads every YAML fixture under
openarmature-spec/spec/<capability>/conformance/ into a typed
pydantic config. Phases 1+ add runtime interpretation under
harness/runtime/ without re-touching parsing.

Bumps the spec submodule to v0.8.0 (8 accepted proposals: foundation,
explicit subgraph mapping, observer hooks, llm-provider, middleware,
fan-out, OTel, checkpointing).

Harness package layout (tests/conformance/harness/):
  - fixtures.py      Three top-level discriminated variants
                     (LlmProviderFixture | CasesFixture |
                     GraphFixture). Discriminator picks by presence
                     of `mock_provider` / `cases:` keys.
  - directives.py    Node directive sub-models with mutual-exclusion
                     validator on the 13 primary directives.
                     Middleware discriminated union over the 5 types
                     in fixtures.
  - expectations.py  Per-capability expected-block discriminator
                     (graph_engine | llm_provider |
                     pipeline_utilities | observability) chosen by
                     which assertion keys appear.
  - loader.py        Auto-discovers NNN-*.yaml across all four
                     capability directories.
  - skip.py          Structured SkipReason with capability +
                     directive list + phase mapping.
  - runtime/         Empty stub package + README locking in the
                     Phase 0 boundary.

Strictness contract: strict (extra="forbid") at the structural
skeleton (top-level fixture, StateSchema, NodeSpec primary directive
set, ObserverSpec, MiddlewareConfig). Permissive (extra="allow") for
payload-shape models (LLM mock responses, middleware params, flaky
config, case shapes) — those evolve frequently in the spec without
restructuring the directive surface.

Tests added (test_fixture_parsing.py): every fixture parses (68)
AND round-trips (parse → model_dump → re-parse → equal). 137
assertions total. Phase 0 exit criterion.

test_conformance.py: existing graph-engine runtime tests still pass
for fixtures the legacy adapter can translate. Fixtures using the
v0.6 pair model or new node directives (fan_out, flaky variants,
calls_llm, update_pure*, emits_log, etc.) skip with phase-tagged
reasons.

Result: 204 pass, 7 skip, 0 fail.

Author: chris-colinsky

openarmature-spec

@@ -0,0 +1,36 @@
+"""Conformance fixture harness — typed parsing for the four spec capabilities.
+
+Phase 0 (per the implementation plan): every fixture under
+``openarmature-spec/spec/<capability>/conformance/`` lands as a typed pydantic
+config. Phases 1–6 add runtime interpretation under ``harness/runtime/``;
+they never re-touch parsing.
+
+Public surface:
+
+- :func:`loader.load_fixture` — parse one YAML path into a typed fixture.
+- :func:`loader.discover_fixtures` — auto-discover fixture paths across the
+  four capability directories on the spec submodule.
+- :class:`fixtures.Fixture` — the root discriminated union
+  (``LlmProviderFixture | CasesFixture | GraphFixture``).
+- :class:`skip.SkipReason` — structured "fixture needs directives X, current
+  phase doesn't support them" used by the test runner to skip cleanly.
+"""
+
+from .fixtures import (
+    CasesFixture,
+    Fixture,
+    GraphFixture,
+    LlmProviderFixture,
+)
+from .loader import discover_fixtures, load_fixture
+from .skip import SkipReason
+
+__all__ = [
+    "CasesFixture",
+    "Fixture",
+    "GraphFixture",
+    "LlmProviderFixture",
+    "SkipReason",
+    "discover_fixtures",
+    "load_fixture",
+]