fix(python): use wrapping_add(1) in seqlock_begin_write for overflow consistency

[SaitejaKommi]

Summary

Use wrapping_add(1) in seqlock_begin_write to provide consistent overflow handling for the seqlock generation counter.

Fixes #2865

Root Cause

In apis/python/node/src/lib.rs, seqlock_begin_write incremented the generation counter using pre_write_gen + 1, while seqlock_end_write already used pre_write_gen.wrapping_add(2).

Using normal integer addition can panic on u64 overflow in debug builds or when overflow checks are enabled, resulting in inconsistent overflow behavior between the begin and end write paths.

Solution

• Replaced pre_write_gen + 1 with pre_write_gen.wrapping_add(1) in seqlock_begin_write.
• Align the overflow behavior with seqlock_end_write, ensuring the generation counter wraps consistently without panicking.

Testing

• ✅ cargo fmt --all -- --check
• ✅ cargo check -p dora-node-api-python

Scope

This PR is intentionally limited to apis/python/node/src/lib.rs and changes a single arithmetic operation to ensure consistent overflow handling. No functional APIs or runtime behavior were otherwise modified.

[trunk-io]

😎 Merged successfully - details.

[phil-opp]

Automated review by Claude — this is a fully automated review; no human has vetted it.

No issues found. Using wrapping_add(1) here makes the begin path consistent with seqlock_end_write's wrapping_add(2) and avoids a potential debug-build overflow panic on the u64 generation counter. The wrap boundary behaves identically to the end path, so seqlock parity semantics are preserved.

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Generated by Claude Code