Fix CI: resolve ruff and mypy failures introduced by evaluation/PIT/pipeline PR

[Copilot]

• Investigate CI failures (pit-doc-sync guard)
• Fix ruff linting errors and mypy type errors (previous commit)
• Add API docs for new PIT modules: release-rules, resolvers, views, panel, missingness, vintage
• Update mkdocs.yml to include new PIT API doc pages
• Add CHANGELOG entries for new PIT primitives and CI fixes
• Verify pit-doc-sync guard passes locally
• Verify mkdocs build --strict passes
• Verify all 257 tests still pass
• Verify ruff and mypy pass

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[steveya]

@copilot CI/CD still failing, pls fix

[Copilot]

@copilot CI/CD still failing, pls fix

Fixed in commit fa0530d. The remaining CI failure was in the pit-doc-sync job: the guard script requires both CHANGELOG and PIT docs updates whenever PIT code is changed. Added API docs for the 6 new PIT modules introduced in the base PR (release rules, vintage resolvers, views, panel builder, missingness, vintage utilities), updated mkdocs.yml with the new nav entries, and added corresponding CHANGELOG entries. The pit-doc-sync guard now passes locally.