[ninglinLiu]

Which issue does this PR close?

• Closes proto: recursion protection for physical plan serde #26738.

Rationale for this change

Converting a physical plan or physical expression to and from protobuf recurses once per nesting level, but unlike logical plan serialization (#23823 / #24124) none of these functions had a recursive stack-growth checkpoint. A deeply nested physical plan or expression could therefore abort the process with a native stack overflow, even when recursive_protection is enabled.

What changes are included in this PR?

Adds #[cfg_attr(feature = "recursive_protection", recursive::recursive)] to the four recursive entry points of physical serde:

• PhysicalPlanNodeExt::try_from_physical_plan_with_converter (plan serialization)
• PhysicalPlanNodeExt::try_into_physical_plan_with_context (plan deserialization)
• serialize_physical_expr_with_converter (expression serialization)
• parse_physical_expr_with_converter (expression deserialization)

Every child plan / child expression goes through these functions, including the default PhysicalProtoConverterExtension hooks, so this covers the whole recursion. The recursive dependency and recursive_protection feature already exist in datafusion-proto, so there are no Cargo changes.

What is the testing strategy for this PR?

Added two tests to datafusion/proto/tests/cases/stack_safety.rs (gated on recursive_protection, like the existing growable-stack test) that round-trip, on a 2 MiB thread stack, a plan of 2,000 nested GlobalLimitExecs and an expression of 2,000 nested NotExprs. They reuse the existing child-process harness (generalised into run_in_child_with) so a regression shows up as a test failure instead of aborting the test binary.

Without the source change both new tests fail with thread 'two-megabyte-stack' has overflowed its stack; with it they pass:

cargo test -p datafusion-proto --features recursive_protection --test proto_integration stack_safety

cargo clippy -p datafusion-proto --all-targets --features recursive_protection -- -D warnings and cargo fmt are clean.

Are there any user-facing changes?

No API changes. With recursive_protection enabled, deeply nested physical plans and expressions now serialize/deserialize instead of overflowing the stack.

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This PR was prepared with AI assistance and reviewed/tested by the author.