[TASK-243] Add subscribe_partition_buckets method and partitions supp…

[fresh-borzoni]

Summary

closes #243

• Add subscribe_partition_buckets method across Rust core, C++ and Python bindings to subscribe to multiple partition+bucket combinations at once
• Add CreatePartition to C++ bindings (was missing, already existed in Python)
• Add partitioned table example to C++ example with CreatePartition, SubscribePartition and SubscribePartitionBuckets usage
• Add subscribe_partition_buckets example to Python example
• Add integration test for subscribe_partition_buckets

[fresh-borzoni]

@luoyuxia @leekeiabstraction PTAL 🙏

[Copilot]

Pull request overview

This PR adds first-class support for subscribing to multiple (partition_id, bucket_id) pairs in one call (subscribe_partition_buckets) across the Rust core API and the C++/Python bindings, plus supporting examples and an integration test. It also fills a gap in the C++ bindings by exposing CreatePartition so partitioned-table workflows can be demonstrated end-to-end.

Changes:

• Add subscribe_partition_buckets to Rust scanners (record + batch) and expose it via C++/Python bindings.
• Add CreatePartition to C++ bindings and wire it through the Rust CXX bridge.
• Extend C++/Python examples and add an integration test validating batch partition subscription behavior.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
crates/fluss/tests/integration/log_table.rs	Adds integration coverage for subscribe_partition_buckets on partitioned tables
crates/fluss/src/client/table/scanner.rs	Implements subscribe_partition_buckets and updates partitioned-table error messaging
bindings/python/src/table.rs	Exposes subscribe_partition_buckets on Python LogScanner and updates to_* docs/errors
bindings/python/fluss/init.pyi	Adds typing stub for subscribe_partition_buckets
bindings/python/example/example.py	Demonstrates subscribe_partition_buckets usage for partitioned table scans
bindings/cpp/src/table.cpp	Adds C++ wrapper call LogScanner::SubscribePartitionBuckets
bindings/cpp/src/lib.rs	Extends CXX bridge with partition subscriptions + create_partition plumbing
bindings/cpp/src/admin.cpp	Implements Admin::CreatePartition in the C++ binding
bindings/cpp/include/fluss.hpp	Adds PartitionBucketSubscription struct and declares new APIs
bindings/cpp/examples/example.cpp	Adds a partitioned-table example using CreatePartition and batch subscriptions

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[luoyuxia]

@fresh-borzoni hi, could you please rebase main branch?

[fresh-borzoni]

@luoyuxia Rebased

[luoyuxia]

@fresh-borzoni Thanks for the pr. LGTM overall, Left minor comments.

[fresh-borzoni]

@luoyuxia TY for the review.
Addressed comments, PTAL 🙏

[luoyuxia]

@fresh-borzoni Thanks for the pr. LGTM!