test: integration tests for reorg tracking in RPC subscriptions and filters (#99)

* test: add integration tests for reorg tracking in RPC subscriptions and filters

Adds 7 integration tests verifying end-to-end reorg handling across the
RPC layer: block tag rewind, polling filter watermark reset, push
subscription removed-log emission, filter selectivity, and a
no-regression check for normal block progression.

Closes ENG-1972

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* test: add multi-block reorg and watermark min() coverage

Address review feedback: strengthen reorg integration tests with
multi-block reverts and multiple-reorgs-between-polls scenarios.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix: update integration tests for ring buffer reorg design

The ring buffer design now correctly returns removed logs on
early-return paths (start > latest) instead of silently discarding
them. Update test_multi_block_reorg_log_filter and
test_multiple_reorgs_between_polls to expect the removed logs.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: prestwich