fix(convert_salary_excel): store standalone count columns as counts, not indexes (#230)

An unmatched count column (e.g. a lone total headcount with no paired index
column) was appended as an untyped standalone value and stored under "index",
even though detect_column_type had already classified it as a count.
salary_lookup then rendered the raw headcount as a salary index with a
meaningless "vs baseline" percentage.

Tag unmatched count columns with field="count" so the row parser stores them
under "count" (as an int, matching the paired-count branch). Standalone index
and untyped columns are unaffected.

tools/convert_salary_excel.py

@@ -168,10 +168,14 @@ def parse_sheet(ws, sheet_label=None):
                 used_indexes.add(ii)
                 break
 
-    # Remaining unmatched count columns become standalone (use original header)
+    # Remaining unmatched count columns become standalone. They are still count
+    # data, so tag them as such — otherwise a lone headcount would be emitted as
+    # a salary index and rendered with a meaningless "vs baseline" percentage.
     for ci, (c_idx, c_header, _) in enumerate(count_cols):
         if ci not in used_counts:
-            categories.append({"name": c_header.lower().replace(" ", "_"), "value_col": c_idx})
+            categories.append(
+                {"name": c_header.lower().replace(" ", "_"), "value_col": c_idx, "field": "count"}
+            )
 
     # Remaining unmatched index columns become standalone (use original header)
     for ii, (i_idx, i_header, _) in enumerate(index_cols):
@@ -226,7 +230,8 @@ def parse_sheet(ws, sheet_label=None):
                         # Non-numeric standalone value (e.g. a free-text "Notes"
                         # column) is not salary data; skip it for this row.
                         continue
-                    entry["categories"][cat_name] = {"index": val}
+                    field = cat.get("field", "index")
+                    entry["categories"][cat_name] = {field: int(val) if field == "count" else val}
 
         companies.append(entry)