Implement fan-out degrade contribution (proposal 0066)

[chris-colinsky]

Summary

Adopts proposal 0066 (spec v0.56.0): a degraded fan-out instance is a success whose contribution is its degraded_update, read in subgraph-field-name space. The submodule advances v0.55.1 to v0.56.0 and conformance.toml marks 0066 implemented.

Engine

• extra_outputs keying fix. The per-instance partial is now uniformly subgraph-keyed across _extract_instance_partial, the accumulator, _rolled_forward_partial (resume), and both _fan_in_* functions, so a degrade's subgraph-space degraded_update composes through the same fan-in. This fixes a latent bug: an instance degraded_update's extra_outputs values were looked up by the parent field name and silently dropped (collect_field was unaffected, which is why fixture 064 with no extra_outputs didn't surface it).
• Compile-time check. A static degraded_update on a fan-out instance FailureIsolationMiddleware that omits collect_field now raises FanOutDegradedUpdateMissingCollectField. A callable degraded_update is exempt (its output isn't knowable at construction).
• Null slot. A callable degraded_update that omits collect_field yields a graceful null slot (the fan-in reads via .get), never a degrade-time raise; the positional collection slot is preserved.

Harness

Fixture 065-fan-out-failure-isolation-degrade-contribution (four cases) is wired into the pipeline-utilities runner: the runner gained expected_compile_error handling for a cases-shape graph: block, and the adapter gained the any fixture type for Case 3's list<any> null-slot collection.

Scope

Success-path and resume behavior for correctly-configured fan-outs is unchanged; the existing fan-out and checkpoint fixtures stay green. The parallel-branches counterpart (Case 4) was already correct from the prior parallel-branches fix and is now pinned by fixture 065.

Validation

• uv run pytest tests/: 1301 passed, 376 skipped
• uv run pytest "tests/conformance/" -k 065: four cases pass
• uv run ruff check ., uv run pyright: clean
• uv run python scripts/check_conformance_manifest.py: 61/61
• uv run mkdocs build: clean

[Copilot]

Pull request overview

Implements openarmature-spec proposal 0066 (spec v0.56.0) by updating fan-out failure-isolation degrade semantics so a degraded instance is treated as a success whose contribution is its degraded_update in subgraph-field-name space, and updates the conformance harness + pins to v0.56.0.

Changes:

• Fix fan-out extra_outputs handling to consistently read per-instance partials in subgraph space and project into parent fields during fan-in (including resume/rolled-forward paths).
• Add a compile-time validation error (FanOutDegradedUpdateMissingCollectField) for static per-instance degraded_update mappings that omit collect_field.
• Extend conformance runner/type adapter to support fixture 065 patterns (expected_compile_error, any type), and bump spec version pins/docs.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/test_smoke.py	Updates spec version assertion to v0.56.0.
tests/conformance/test_pipeline_utilities.py	Adds compile-error case handling and includes fixture 065 in the driven set.
tests/conformance/adapter.py	Adds any fixture type support for null-slot collection cases.
src/openarmature/graph/fan_out.py	Aligns per-instance partials and fan-in/out logic with proposal 0066 (subgraph-space partials, .get for null slots).
src/openarmature/graph/errors.py	Introduces FanOutDegradedUpdateMissingCollectField compile error category.
src/openarmature/graph/builder.py	Adds compile-time check for static degraded_update missing collect_field.
src/openarmature/graph/init.py	Re-exports the new compile error in the public API.
src/openarmature/AGENTS.md	Updates referenced spec version to v0.56.0.
src/openarmature/init.py	Bumps __spec_version__ to v0.56.0.
pyproject.toml	Bumps [tool.openarmature].spec_version to v0.56.0.
conformance.toml	Pins spec to v0.56.0 and marks proposal 0066 as implemented.
CHANGELOG.md	Documents proposal 0066 behavior and the spec pin bump to v0.56.0.

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