Removes the `instrument_id: 0` backward-compat default introduced in 6c1ab8850.
That default was nonsensical: a sentinel value for an identifier creates the
exact half-state that future filtering code can't distinguish from real data.
Now extract_trades_from_snapshots takes `instrument_id: u32` as an explicit
required parameter. Caller must provide the contract id the snapshot stream
belongs to (typically captured at the data-acquisition site alongside symbol).
Tests:
- test_extract_trades_from_snapshots updated to pass id=12345 + asserts every
emitted trade carries that id (verifies the explicit-param contract).
- New test_filter_front_month_mbp10_picks_highest_volume covers the helper
added in 6c1ab8850 (no test before).
- New test_filter_front_month_mbp10_empty for the empty-input edge case.
15/15 mbp10 tests pass. Workspace + examples compile clean.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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