fix(pdf): require non-empty description; tighten multi-line merge

User reported "Daily Ledger Balances" entries leaking into
output. Three correlated bugs in the row qualifier:

**1. Empty description is now disqualifying.** A row like
``01/13/2025  $1,000.00`` has a date and an amount but no text
between them — that's a daily-balance entry, a period-summary,
or page furniture. Drop these. New filter sits after
``_description_from_row`` returns: if the description string is
empty (or whitespace-only), continue past the row.

**2. ``prev`` resets per page.** The state that drives multi-
line description merging (the "previous transaction this
continuation might attach to") used to persist across page
boundaries. A no-date no-amount line at the top of page 2
could silently attach to the last transaction on page 1. Fixed
by moving the ``prev`` / ``prev_y_bottom`` declarations into
the outer page loop so each page starts clean.

**3. Multi-line merges now check y-distance.** Before this fix,
ANY no-date no-amount line attached to the previous
transaction's description. A "Daily Ledger Balances" section
header several rows below the last transaction would silently
fold into it. Now the merge only happens when the gap
``current_top - prev_y_bottom <= 25.0`` PDF points — generous
enough for one blank-line gap between wrapped descriptions,
tight enough to reject section headers across paragraph
breaks. The threshold is a module constant
(``_MULTILINE_MERGE_MAX_GAP``) for future tuning if real
statements call for it.

Three new test classes:

- ``TestRequiresDescription.test_empty_description_row_dropped``
  — date+amount-no-text row filtered, real transaction kept.
- ``TestPrevTransactionResetsPerPage.test_no_cross_page_merge``
  — page-1 transaction + page-2 section header = no merge.
- ``TestMultilineMergeYGap`` — close continuation merges
  (10-pt gap), far section header doesn't (100-pt gap).

The original ``TestMultilineDescription.test_continuation_line_merges``
still passes — its setup has a 10-pt gap which is within the
new threshold.

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

src/pdf_extract.py

@@ -778,9 +778,21 @@ def scan_pdf_for_transactions(
     metadata = extract_statement_metadata(pages)
 
     out_rows: list[dict[str, Any]] = []
-    prev: dict[str, Any] | None = None
+    # Maximum y-gap (in PDF points) between a transaction and a
+    # following no-date-no-amount line for that line to count as a
+    # continuation of the description. Typical line baselines sit
+    # ~10–14 pts apart; 25 pts allows for one blank line but
+    # rejects section headers that are several rows away.
+    _MULTILINE_MERGE_MAX_GAP = 25.0
 
     for page in pages:
+        # ``prev`` and ``prev_y_bottom`` reset per page so a section
+        # header at the top of page 2 can't attach to the last
+        # transaction on page 1 — PDF y-coordinates restart at the
+        # top of each page so the y-distance check is meaningless
+        # across page boundaries.
+        prev: dict[str, Any] | None = None
+        prev_y_bottom: float | None = None
         rows = cluster_rows(page.words, y_tolerance=y_tolerance)
         for row_words in rows:
             line = " ".join(w.text for w in row_words).strip()
@@ -791,18 +803,29 @@ def scan_pdf_for_transactions(
             amount_tokens = _find_amount_tokens(row_words)
 
             if not dates or not amount_tokens:
-                # Continuation candidate — a line on a transaction
-                # page that has neither a date nor an amount of its
-                # own. Attach to the previous row's description.
+                # Continuation candidate — a line with no date AND
+                # no amount of its own. Only attach to the previous
+                # transaction if (a) we have one, (b) it's on this
+                # same page, and (c) the y-gap to it is small enough
+                # that a human would read this as a wrapped line
+                # rather than a separate paragraph or section header.
                 if (
                     merge_multiline_descriptions
                     and prev is not None
                     and not dates
                     and not amount_tokens
+                    and row_words
                 ):
-                    prev["description"] = (
-                        (prev["description"] + " " + line).strip()
-                    )
+                    current_top = min(w.top for w in row_words)
+                    if (
+                        prev_y_bottom is not None
+                        and (current_top - prev_y_bottom)
+                        <= _MULTILINE_MERGE_MAX_GAP
+                    ):
+                        prev["description"] = (
+                            (prev["description"] + " " + line).strip()
+                        )
+                        prev_y_bottom = max(w.bottom for w in row_words)
                 continue
 
             # First date wins for the "date" column; ALL dates are
@@ -816,6 +839,14 @@ def scan_pdf_for_transactions(
                 row_words, date_ranges, amount_idxs,
             )
 
+            # Every real transaction must have a description. Rows
+            # like "01/13/2025  $1,000.00" (Daily Ledger Balances
+            # section, page totals, period summaries) carry a date
+            # and an amount but no text in between — they're
+            # statement furniture, not transactions. Drop them.
+            if not desc.strip():
+                continue
+
             iso = parse_date(first_date_text, date_formats)
             if iso is None:
                 # Short date — try to bind to the statement period
@@ -867,6 +898,9 @@ def scan_pdf_for_transactions(
 
             out_rows.append(record)
             prev = record
+            prev_y_bottom = (
+                max(w.bottom for w in row_words) if row_words else None
+            )
 
     return out_rows, warnings