[truealpha-factors] Freeze safe Qlib expression corpus

[wangzitian0]

Scope

Freeze the preparation-only S8 corpus for #189. This PR contains no contract or compiler implementation and earns no evidence rung.

The corpus pins:

• the isolated pyqlib==0.9.7 runtime and lock identities;
• a builtin-only six-operator registry with exact argument, null, and lookback semantics;
• three typed expressions over two synthetic instruments and five sessions;
• malicious-input, identity-drift, Decimal-context, and root-lock negative controls.

During preparation, direct Qlib execution confirmed that Mean(..., N) uses min_periods=1; the frozen contract therefore declares null behavior per operator instead of claiming global null propagation. The #189 design body was corrected accordingly.

Verification

• make issue-graph-check
• frozen runtime pyqlib==0.9.7 parsed and executed all three compiled fields; every value and null position matched the independent fixture oracle at 1e-12 tolerance
• fixture/runtime/spec SHA-256 identities verified
• git diff --check

Issue: #189

[wangzitian0]

@copilot review

[Copilot]

Pull request overview

Freezes the preparation-only S8 “safe Qlib factor-expression” corpus for issue #189 by pinning the corpus bytes and updating governance metadata to mark the batch as prepared, without advancing any evidence rung or introducing contract/compiler implementation.

Changes:

• Adds a pinned JSON corpus fixture (qlib_expression.v1.json) defining the operator registry, feature bindings, typed expression cases, expected compiled fields, and negative controls.
• Advances the S8 batch manifest from queued→prepared (revision 2) and pins activation.base_sha plus the corpus manifest path and SHA-256.
• Updates the Vision issue graph entry for S8 to reflect the prepared status and new manifest hash.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
libs/contracts/tests/fixtures/qlib_expression.v1.json	Introduces the frozen S8 typed-expression corpus fixture (operators, expressions, expected outputs, negative cases).
governance/vision-issue-graph.json	Marks S8 as prepared and updates the manifest SHA-256 pointer in the Vision graph.
governance/batches/S8-qlib-factor-expression.v1.json	Updates S8 manifest to revision 2 / prepared, pinning base SHA and corpus path+hash for the preparation freeze.

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