Add read model abstraction

[PANiXiDA]

What changed

• added the public abstract ReadModel record in PANiXiDA.Core.Application.Querying;
• added a unit test demonstrating record-based inheritance;
• updated query examples and repository guidance to keep Domain types out of read-side contracts.

Why

Application read repositories and query handlers need a common marker for immutable read-side result payloads. Naming alone cannot reliably distinguish a read model from an arbitrary DTO, while the base type enables consumer architecture tests without coupling the read side to Domain types.

Impact

Consumers can derive query and read repository result models from ReadModel. Existing APIs remain source-compatible because this is an additive public API change.

Validation

• dotnet restore
• dotnet format
• dotnet build --configuration Release — 0 warnings, 0 errors
• dotnet test --configuration Release — 48/48 passed

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 64f78ac329

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[chatgpt-codex-connector]

Use read models in the pagination examples

The newly documented boundary says pagination models should contain ReadModel payloads, but the immediately following page and cursor examples still use PaginationResult<string> and CursorPaginationResult<string>. Consumers following these examples will therefore adopt the exact primitive-result pattern this change discourages; update both examples to contain a record derived from ReadModel.

AGENTS.md reference: AGENTS.md:L63-L64

Useful? React with 👍 / 👎.