Phase 5/6. Adds a "Visual picker" tab as the first stop in the
template-build flow. The sample PDF page is rasterized with
``pypdfium2`` (capped at ~900px wide for sensible display), and
``streamlit-drawable-canvas`` overlays drawing tools on top.
UX:
- **Line mode** — drag short (roughly vertical) strokes where you
want columns to split. Each stroke's x-midpoint becomes one
boundary in PDF point coordinates.
- **Rect mode** — drag a rectangle around the transactions
table; bbox is preserved on the template as
``visual.table_bbox`` for round-trip, future use as a hard
crop region.
- **Transform mode** — move/resize already-drawn shapes after
the fact.
Round-trip: re-entering Build mode with an existing template
seeds the canvas with full-height vertical lines for every
boundary already on the template, plus the saved bbox if any,
so editing-after-save matches the user's mental model.
Coordinate translation: the canvas reports pixel positions; we
divide by the renderer's pixels-per-PDF-point scale to get back
to PDF coordinates that ``apply_template`` already expects. No
template-schema change required — the boundaries the picker
writes are the same list the text-input editor wrote in
commit 3, just sourced visually.
New helper in the extraction module:
- ``render_page_image(pdf_bytes, page_no, target_width=900)`` —
rasterize a single 1-indexed page to a PIL image; returns
``(image, scale)`` for coordinate translation.
The text-input boundary editor in the Columns tab remains as a
fallback for power users / keyboard-only workflows and for
copy-paste from spreadsheet-derived x-positions.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Michael
b86828d791