feat(sql): lower IN subqueries into joins

[Treasure520520]

/claim #1659

Proposed Changes

This PR adds a scoped first implementation for the remaining IN (SELECT ...) streaming SQL path:

• Detects single-column Expr::InSubquery predicates in the SQL pipeline builder.
• Lowers lhs IN (SELECT rhs FROM ...) into the existing join pipeline by creating an inner join on lhs = subquery_alias.rhs.
• Reuses the existing JoinProcessorFactory and current join ports instead of introducing a new processor.
• Qualifies an unqualified outer identifier with the outer table/alias when available, so customer_id IN (...) can resolve against the left side of the generated join.
• Rejects multi-column IN subqueries and NOT IN (SELECT ...) explicitly instead of silently building an unsupported selection expression.

Demo

Short demo asset: https://github.com/Treasure520520/dozer/releases/download/dozer-1659-demo-2489/dozer-1659-in-subquery-demo.gif

Proof

Added builder regression coverage:

• test_in_subquery_is_lowered_into_pipeline_inputs checks that a query with orders.customer_id IN (SELECT allowed_customers.customer_id FROM allowed_customers) builds a pipeline that pulls both orders and allowed_customers as inputs and registers the requested output table.
• test_in_subquery_rejects_multi_column_projection checks that multi-column subquery projections fail early with UnsupportedSqlError.

Validation

Passed locally:

PATH=/Users/treasure/Documents/Codex/2026-05-12/goal-100-paypal-puresenses2021-gmail-com/tools/rustup/toolchains/1.91.1-aarch64-apple-darwin/bin:$PATH rustfmt --check dozer-sql/src/builder/mod.rs dozer-sql/src/builder/tests.rs
git diff --check

Attempted but blocked by local macOS toolchain setup before crate compilation:

PATH=/Users/treasure/Documents/Codex/2026-05-12/goal-100-paypal-puresenses2021-gmail-com/tools/rustup/toolchains/1.91.1-aarch64-apple-darwin/bin:$PATH cargo test -p dozer-sql builder::tests::test_in_subquery --no-default-features

The failure occurs while linking dependency build scripts (libc, serde, proc-macro2, etc.) with cc, with exit status 69 and the message: You have not agreed to the Xcode license agreements. No project crate type-checking was reached on this machine.

Checklist

• PR created against the default branch
• Tests added for the new builder behavior
• Formatting for touched files checked
• Validation blockers documented

[CLAassistant]

All committers have signed the CLA.

[Treasure520520]

Adding the short demo asset requested by the Algora bounty guidelines:

Demo GIF: https://github.com/Treasure520520/dozer/releases/download/dozer-1659-demo-2489/dozer-1659-in-subquery-demo.gif

It summarizes the scoped IN (SELECT ...) builder lowering, the positive/negative regression coverage, and the current local validation status (rustfmt --check and git diff --check passed; focused cargo test remains blocked on this machine by the unsigned Xcode license before crate compilation).

The remaining external blocker I can see is the CLA status.

[Treasure520520]

CLA is now signed. The demo GIF and validation notes are in the PR body, so this is ready for maintainer review from my side. Thanks!