fix(pdf): drop zero-amount rows; multi-date rows clean description

Two corrections from real-statement feedback:

**1. Drop rows where the transaction amount is exactly 0.**
Bank statements include date+amount-shaped noise like
"INTEREST EARNED 0.00", "PAGE TOTAL 0.00", "BALANCE FORWARD
0.00 1,234.56" — all match the date+amount heuristic but
aren't transactions. New filter in
``scan_pdf_for_transactions``: drop rows whose ``amount_1``
parses to exactly 0. Non-zero balances in ``amount_2`` don't
rescue a zero amount_1 — leftmost amount is the canonical
transaction amount. Unparsed-but-non-empty amount strings are
kept (user verifies in the editor).

**2. Multi-date rows: first date wins for the column, every
date excluded from the description.** Chase / BofA / Wells
commonly show both a transaction date and a posting date per
row:

    01/13  01/14  COFFEE SHOP  $4.50

Before this fix, ``_find_dates_in_words`` returned the first
date only and the second date leaked into description as
"01/14 COFFEE SHOP". Now it returns ALL dates with their word
ranges; the scanner uses ``dates[0]`` as the canonical date
and passes every range to the description builder for
exclusion.

The detector's two-pass strategy now also guards against
mixing full-year and short-date matches on the same row.
Previously, a header line like ``Page 1/2 of 3 ... Statement
Date 01/13/2026`` would return both ``1/2`` and ``01/13/2026``,
and ``1/2`` (being leftmost) would have won the date column.
Now: if any full-year date is found on the row, short patterns
are NOT also collected — full year anchors interpretation. A
row with no full-year date (Chase short-date case) still falls
back to short patterns and collects all of them.

New tests:
- ``test_multiple_dates_returned_in_position_order`` —
  ``01/13`` + ``01/14`` both returned, in order
- ``TestMultiDateRow.test_first_date_wins_second_excluded_from_description``
  — end-to-end through ``scan_pdf_for_transactions``
- ``TestZeroAmountRowsAreDropped.test_zero_amount_row_dropped``
  — "INTEREST EARNED 0.00" row dropped while real txn kept
- ``test_negative_amount_kept`` — pin that -40.00 is not
  treated as zero by the filter

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/test_pdf_extract_smoke.py

@@ -144,6 +144,107 @@ class TestScanPdfForTransactions:
 # ---------------------------------------------------------------------------
 
 
+class TestMultiDateRow:
+    """Some statements (Chase, BofA) show both a transaction date
+    and a posting date per row. The scanner uses the first date
+    in position order and excludes every date from the description."""
+
+    def test_first_date_wins_second_excluded_from_description(self):
+        from src import pdf_extract as mod
+        from src.pdf_extract import Page, WordBox, scan_pdf_for_transactions
+
+        original = mod.extract_pages_auto
+
+        def fake(_b, *, allow_ocr=True):
+            words = [
+                WordBox(x0=0, top=0, x1=40, bottom=10, text="01/13"),
+                WordBox(x0=50, top=0, x1=90, bottom=10, text="01/14"),
+                WordBox(x0=100, top=0, x1=160, bottom=10, text="Coffee"),
+                WordBox(x0=170, top=0, x1=210, bottom=10, text="Shop"),
+                WordBox(x0=220, top=0, x1=270, bottom=10, text="$4.50"),
+            ]
+            return [Page(
+                page_no=1, width=300, height=20, text="", words=words,
+            )], []
+
+        mod.extract_pages_auto = fake
+        try:
+            rows, _ = scan_pdf_for_transactions(b"")
+        finally:
+            mod.extract_pages_auto = original
+
+        assert len(rows) == 1
+        # First date used as the canonical
+        assert rows[0]["date"] == "01/13"
+        # Second date NOT in description
+        assert "01/14" not in rows[0]["description"]
+        # Description is the actual content between dates and amount
+        assert rows[0]["description"] == "Coffee Shop"
+
+
+class TestZeroAmountRowsAreDropped:
+    """Rows where the transaction amount is exactly 0 are noise
+    (statements love to print "INTEREST EARNED 0.00" or
+    "PAGE TOTAL 0.00") and get filtered out."""
+
+    def test_zero_amount_row_dropped(self):
+        from src import pdf_extract as mod
+        from src.pdf_extract import Page, WordBox, scan_pdf_for_transactions
+
+        original = mod.extract_pages_auto
+
+        def fake(_b, *, allow_ocr=True):
+            words = [
+                # Real transaction
+                WordBox(x0=0, top=0, x1=80, bottom=10, text="01/13/2026"),
+                WordBox(x0=100, top=0, x1=160, bottom=10, text="Coffee"),
+                WordBox(x0=200, top=0, x1=240, bottom=10, text="$4.50"),
+                # Zero-amount noise row (should be dropped)
+                WordBox(x0=0, top=20, x1=80, bottom=30, text="01/14/2026"),
+                WordBox(x0=100, top=20, x1=180, bottom=30, text="INTEREST"),
+                WordBox(x0=200, top=20, x1=240, bottom=30, text="0.00"),
+            ]
+            return [Page(
+                page_no=1, width=300, height=40, text="", words=words,
+            )], []
+
+        mod.extract_pages_auto = fake
+        try:
+            rows, _ = scan_pdf_for_transactions(b"")
+        finally:
+            mod.extract_pages_auto = original
+
+        assert len(rows) == 1
+        assert rows[0]["amount_1"] == 4.50
+        assert "INTEREST" not in rows[0]["description"]
+
+    def test_negative_amount_kept(self):
+        from src import pdf_extract as mod
+        from src.pdf_extract import Page, WordBox, scan_pdf_for_transactions
+
+        original = mod.extract_pages_auto
+
+        def fake(_b, *, allow_ocr=True):
+            words = [
+                WordBox(x0=0, top=0, x1=80, bottom=10, text="01/13/2026"),
+                WordBox(x0=100, top=0, x1=160, bottom=10, text="Withdraw"),
+                WordBox(x0=200, top=0, x1=240, bottom=10, text="(40.00)"),
+            ]
+            return [Page(
+                page_no=1, width=300, height=20, text="", words=words,
+            )], []
+
+        mod.extract_pages_auto = fake
+        try:
+            rows, _ = scan_pdf_for_transactions(b"")
+        finally:
+            mod.extract_pages_auto = original
+
+        # -40 is not zero — keep it
+        assert len(rows) == 1
+        assert rows[0]["amount_1"] == -40.00
+
+
 class TestMultilineDescription:
     def test_continuation_line_merges(self):
         """A line with no date and no amount, sitting between two