Cover fan-out degrade refinements (0069)

[chris-colinsky]

Summary

Adopts proposal 0069 (spec v0.59.0), which refines 0066's fan-out degrade contribution rules. python's runtime already satisfied all three refinements, so this PR is conformance coverage with no library behavior change.

The three refinements (all already conformant):

1. An omitted extra_outputs source contributes a positional null slot (index-aligned with target_field), not "not contributed".
2. An absent collect_field on any fan-in path is a null slot and the fan-in does not raise, with the caveat that under a strict-element reducer (concat_flatten / merge_all) a null contribution still raises ReducerError. python does not suppress it: the reducer runs in the engine merge, downstream of the fan-in.
3. A degraded slot survives a checkpoint + resume round-trip.

Third of four PRs folding the v0.14.0 consolidated spec-review findings (0068 through 0071) into the release.

Changes

• Fixture 069 split. 069 is a mixed fixture: its FI-degrade cases (1-2) run in the pipeline-utilities runner; its degrade + crash_injection + resume case (3) runs in the checkpoint runner. The two runners partition cases on a checkpointer / resume / crash_injection marker. The checkpoint runner gains a small static-degrade FailureIsolationMiddleware translator (the only degrade shape its fixtures use; the callable forms stay with pipeline-utilities) and leaves non-failure_isolation instance middleware unwired, as before.
• Strict-reducer unit test. A callable degrade that nulls a slot under concat_flatten raises ReducerError (callable form because a static degrade omitting collect_field is a 0066 compile error).
• Pin to v0.59.0: conformance.toml (spec_pin + [proposals."0069"]), the three spec-version sync points, regenerated AGENTS.md; CHANGELOG pin-summary.

Testing

• uv run pytest tests/: 1320 passed, 376 skipped.
• ruff and pyright clean.
• Verified the split partitions every case to exactly one runner (no silently-skipped checkpoint fixtures).

[Copilot]

Pull request overview

Updates the repo to openarmature-spec v0.59.0 (proposal 0069) and adds conformance coverage for the refined fan-out degrade contribution rules, without changing runtime library behavior.

Changes:

• Added a focused unit test asserting ReducerError when a degraded (null) slot hits a strict-element reducer (concat_flatten).
• Split fixture 069 coverage across runners by skipping checkpoint-concern cases in test_pipeline_utilities.py and adding fixture 069 to the checkpoint runner (plus a minimal FI instance-middleware translator there).
• Bumped spec pin/version sync points to v0.59.0 and recorded proposal 0069 in conformance.toml and the changelog.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tests/unit/test_fan_out.py	Adds strict-reducer degrade/null-slot unit coverage for proposal 0069 caveat.
tests/test_smoke.py	Updates __spec_version__ assertion to 0.59.0.
tests/conformance/test_pipeline_utilities.py	Includes fixture 069 and skips checkpoint-concern cases in this runner.
tests/conformance/test_checkpoint.py	Includes fixture 069 checkpoint case handling and translates FI instance middleware (static form).
src/openarmature/AGENTS.md	Regenerates bundled agent doc header for spec v0.59.0.
src/openarmature/init.py	Updates __spec_version__ to 0.59.0.
pyproject.toml	Updates tool.openarmature.spec_version to 0.59.0.
conformance.toml	Pins spec to v0.59.0 and marks proposal 0069 as implemented.
CHANGELOG.md	Updates the consolidated spec-pin summary to include v0.59.0 / proposal 0069.

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