feat(analysis): accept write values that bind no placeholder

[omer-cengel]

Summary

Common write idioms such as updated_at = now(), version = version + 1, DEFAULT, literals, and NULL were rejected because every INSERT value and UPDATE assignment had to be a placeholder. They are now accepted as written: a value that binds no placeholder contributes no generated parameter and reaches the database unchanged, while the placeholders beside it keep their existing numbering and binding order.

Changes

• INSERT ... VALUES accepts, for each column, either a placeholder or an expression that binds none; the expression's target column must exist in the table, but its type does not need a Java mapping because nothing binds it.
• UPDATE ... SET accepts the same per assignment; assignment placeholders still bind before WHERE placeholders, for both $N and :name queries.
• A column-list assignment such as SET (name, active) = ('a', TRUE) now fails with UPDATE assignments must set one column at a time.
• A placeholder nested inside a write value, such as $2 || 'x' or COALESCE($2, bio), is rejected as a placeholder in an unsupported location.
• Analyzer tests cover interleaved $N and named placeholders, returning inserts, mixed UPDATE assignments, writes without any placeholder, unmapped-type target columns, unknown target columns, and the rejections; a PostgreSQL integration test generates, compiles, and runs an :exec insert, a returning named insert, and an :exec update using DEFAULT, a literal, NULL, now(), and code + 1.
• The query documentation describes the accepted values, an example with its generated signature and binding order, and the updated rejections.

Scope and non-goals

• Placeholders inside expressions or casts remain rejected.
• ON CONFLICT, multi-row VALUES, and INSERT ... SELECT are unchanged and remain rejected.
• Column references inside a non-binding expression are not resolved; the expression is passed to the database as written.
• SQL parameter compilation, Java generation, and the runtime are unchanged.