chore: backup before code cleanup

Backup commit before executing remove-unused-code proposal.
This includes all pending changes and new features.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

openspec/changes/fix-table-column-alignment/specs/document-processing/spec.md

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+## ADDED Requirements
+
+### Requirement: Table Column Alignment Correction
+The system SHALL correct table cell column assignments using header-anchor alignment when PP-Structure outputs incorrect column indices.
+
+#### Scenario: Correct column shift using header anchors
+- **WHEN** processing a table with cell_boxes and HTML content
+- **THEN** the system SHALL extract header row (row_idx=0) column X-coordinate ranges
+- **AND** validate each cell's column assignment against header X-ranges
+- **AND** correct column index if cell X-overlap with assigned column is < 50%
+- **AND** assign cell to column with highest X-overlap
+
+#### Scenario: Handle tables without headers
+- **WHEN** processing a table without a clear header row
+- **THEN** the system SHALL skip column correction
+- **AND** use original PP-Structure column assignments
+- **AND** log that header-anchor correction was skipped
+
+#### Scenario: Log column corrections
+- **WHEN** a cell's column index is corrected
+- **THEN** the system SHALL log original and corrected column indices
+- **AND** include cell content snippet for debugging
+- **AND** record total corrections per table
+
+### Requirement: Vertical Text Fragment Merging
+The system SHALL detect and merge vertically fragmented Chinese text blocks that represent single cells spanning multiple rows.
+
+#### Scenario: Detect vertical text fragments
+- **WHEN** processing table text regions
+- **THEN** the system SHALL identify narrow text blocks (width/height ratio < 0.3)
+- **AND** filter blocks in leftmost 15% of table area
+- **AND** group vertically adjacent blocks with X-center deviation < 10px
+
+#### Scenario: Merge fragmented vertical text
+- **WHEN** vertical text fragments are detected
+- **THEN** the system SHALL merge adjacent fragments into single text blocks
+- **AND** combine text content preserving reading order
+- **AND** calculate merged bounding box spanning all fragments
+- **AND** treat merged block as single cell for column assignment
+
+#### Scenario: Preserve non-vertical text
+- **WHEN** text blocks do not meet vertical fragment criteria
+- **THEN** the system SHALL preserve original text block boundaries
+- **AND** process normally without merging
+
+## MODIFIED Requirements
+
+### Requirement: Extract table structure
+The system SHALL extract cell content and boundaries from PP-StructureV3 tables, with post-processing correction for column alignment errors.
+
+#### Scenario: Extract table structure with correction
+- **WHEN** PP-StructureV3 identifies a table
+- **THEN** the system SHALL extract cell content and boundaries
+- **AND** validate cell_boxes coordinates against page boundaries
+- **AND** apply header-anchor column correction when enabled
+- **AND** merge vertical text fragments when enabled
+- **AND** apply fallback detection for invalid coordinates
+- **AND** preserve table HTML for structure
+- **AND** extract plain text for translation