fix: update header_results with corrected opening balance

[boscorat]

Summary

_apply_opening_balance_correction() in statements.py correctly updated checks_and_balances, lines_results, and the scalar std_opening_balance — but did not update header_results. Since StatementHeads reads STD_OPENING_BALANCE from header_results to write to parquet/SQLite, the corrected opening balance never reached the database.

This caused the GapReport VIEW to compare the uncorrected (wrong) opening balance against the previous statement's closing balance, producing false GAP flags for Halifax current account statements.

Changes

• statements.py: Update header_results with corrected STD_OPENING_BALANCE in _apply_opening_balance_correction(). Remove redundant scalar assignment (it's derived from header_results at line 560). Add diagnostic print on correction.
• test_opening_balance_correction.py: Add test_correction_updates_header_results. Add header_results to test helper. Update existing tests to derive scalar from header_results post-correction.

Closes

Closes #215

[Copilot]

🟢 Approval recommended

The fix is narrowly scoped to the persistence pathway for corrected opening balances and is backed by targeted tests, with only minor non-blocking nits identified.

Pull request overview

This PR fixes an end-to-end data propagation bug where _apply_opening_balance_correction() corrected the opening balance in internal validation/line results but did not update header_results, so StatementHeads persisted the wrong STD_OPENING_BALANCE to Parquet/SQLite and caused false GAP flags (notably for Halifax statements).

Changes:

• Update _apply_opening_balance_correction() to overwrite header_results.STD_OPENING_BALANCE so downstream persistence uses the corrected value.
• Remove the redundant std_opening_balance scalar assignment (since it is derived from header_results later in Statement.__init__).
• Add/extend tests to ensure header_results and the derived scalar reflect the corrected opening balance.

File summaries

File	Description
src/bank_statement_parser/modules/statements.py	Persist corrected opening balance into header_results so StatementHeads writes the corrected value to Parquet/SQLite; add a diagnostic print.
tests/test_opening_balance_correction.py	Extend helper and add a test to verify the correction updates header_results, and adjust scalar expectations to derive from header_results.

Review details

Suppressed comments (1)

tests/test_opening_balance_correction.py:185

• This test comment references an exact line number in Statement.__init__ ("line 560"), which will drift as the file changes and becomes misleading. Prefer describing the behavior without hard-coding line numbers.

        # Simulate Statement.__init__ line 560: scalar derived from header_results

• Files reviewed: 2/2 changed files
• Comments generated: 2
• Review effort level: Lite

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