docs: add consumer AlephMapper Agent Skill

[ycherkes]

Summary

Add a portable, consumer-facing Agent Skill under .agents/skills/alephmapper/ and document installation from this repository with the Skills CLI.

Scope

• SKILL.md: teach AI coding agents AlephMapper's ordinary C# mapping as the source of truth, its generated companions, when to use [Projectable], [Updatable], and method-level [Adapt], and how to verify the generated output.
• references/projections.md: handwritten and generated expression use, helper inlining, extra factory parameters, predicates and provider translation boundaries.
• references/updates-and-null.md: update-in-place overloads, default collection-skip policy, NullConditionalRewrite.Ignore/Rewrite/None, and safe nullable extension receiver guidance.
• references/adaptation-and-diagnostics.md: explicit compatible-pair adaptation, naming/flags, generated-output inspection and troubleshooting diagnostics.
• README: a short Agent Skill installation section with npx skills add Raffinert/AlephMapper --skill alephmapper.

Important correctness notes

• Treat AlephMapper as a compile-time source generator, not a runtime EF interceptor or convention mapper.
• Its default NullConditionalRewrite.Ignore removes null-conditional checks in generated expressions; choose Rewrite deliberately when null behavior matters.
• The generated update overload's destination argument is currently named dest (shown positionally), and collection updates are opt-in.
• [Adapt] is explicit and method-only; default flags are Map | Expression, Name is required for generated expressions, and generic method adaptation is not supported.
• A generated expression is still subject to the selected LINQ provider's translation capabilities.

Validation

• Checked public README, attribute declarations, emitter implementations, integration tests and adaptation documentation against the skill guidance.
• Verified frontmatter and relative reference paths, README installation command, and five-file diff.
• Documentation-only PR; no production code or test changes. The .NET test suite was not run for this PR.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-12T07:33:38.768282Z	74b424f	PR opened

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