feat(analysis): accept an aliased sole COUNT(*) projection

[omer-cengel]

Summary

A read can now count its matching rows. When COUNT(*) with an alias is the only projection, the query generates a <QueryName>Result record with one non-null Long component named after the alias. Before this change, every COUNT(*) failed with Unsupported SELECT expression: Function, so a common CRUD count query could not be compiled.

Changes

• Query analysis recognises an unqualified, case-insensitive COUNT(*) with an alias written with or without AS. It resolves as a non-null BIGINT column, which generates a Long component that is 0 when no row matches.
• The count works with any supported source, predicate, ordering and pagination shape, and under any result annotation. Its predicate and pagination parameters bind as before.
• COUNT(*) without an alias fails with COUNT(*) requires a result alias, such as COUNT(*) AS total.
• COUNT(*) beside another projection item fails with COUNT(*) must be the only SELECT item.
• New analyzer tests cover the accepted count and every rejected form. A new PostgreSQL integration test compiles a :one count, checks that its component is typed Long, and checks the result for matching and non-matching input.
• The query reference documents the scalar count and its diagnostics. The quickstart's invalid-query example now uses a query that is still rejected.

Scope and non-goals

• COUNT(column), COUNT(DISTINCT ...), COUNT(t.*), a qualified pg_catalog.count(*), the FILTER and OVER forms, and every other function or aggregate still fail with the existing unsupported-expression diagnostic.
• GROUP BY and HAVING are still not analyzed, and RETURNING is unchanged.
• The generator, the query model and the runtime are unchanged. An existing BIGINT result column already generates a Long component.