refactor(dynamic): reorganize type description modules

[schmidma]

Description

GitHub shows this PR against main, but the intended review base is #142.

Rename client-style helpers into query-oriented modules where they are really one-shot query logic, and split extended service and query code out of the large mixed-purpose module.

Behavior is intended to stay unchanged as much as possible. This is primarily an organization pass that makes future maintenance easier by aligning files with responsibilities instead of historical growth.

Checklist

• Ran ./scripts/check-local.sh successfully
• Added or updated tests and documentation when applicable

[codecov]

Codecov Report

❌ Patch coverage is 66.88186% with 513 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
crates/ros-z/src/dynamic/serialization/cdr.rs	28.92%	86 Missing ⚠️
crates/ros-z/src/extended_schema.rs	66.66%	72 Missing ⚠️
crates/ros-z/src/dynamic/value.rs	0.00%	63 Missing ⚠️
...tes/ros-z/src/extended_type_description_service.rs	75.88%	34 Missing ⚠️
crates/ros-z/src/node.rs	68.86%	33 Missing ⚠️
crates/ros-z/src/service.rs	77.77%	32 Missing ⚠️
crates/ros-z/src/action/client.rs	11.76%	30 Missing ⚠️
crates/ros-z/src/graph.rs	72.89%	29 Missing ⚠️
crates/ros-z/src/dynamic/schema.rs	43.47%	26 Missing ⚠️
crates/ros-z/src/dynamic/discovery.rs	80.16%	24 Missing ⚠️
... and 11 more

Files with missing lines	Coverage Δ
crates/ros-z/src/action/server.rs	74.38% <ø> (ø)
crates/ros-z/src/config.rs	81.62% <ø> (ø)
crates/ros-z/src/context.rs	51.19% <100.00%> (+0.59%)	⬆️
...ates/ros-z/src/dynamic/type_description_service.rs	61.61% <100.00%> (+30.93%)	⬆️
crates/ros-z/src/encoding.rs	95.37% <ø> (ø)
crates/ros-z/src/event.rs	87.57% <100.00%> (+0.25%)	⬆️
crates/ros-z/src/lib.rs	100.00% <ø> (ø)
crates/ros-z/src/parameter/client.rs	98.38% <100.00%> (ø)
crates/ros-z/src/parameter/service.rs	78.74% <100.00%> (ø)
crates/ros-z/src/ros_msg.rs	48.64% <100.00%> (+4.53%)	⬆️
... and 22 more

... and 3 files with indirect coverage changes

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