Add --raw flag to csv command to skip aggregation

- Add `to_csv_entries()` to output.py: converts raw rows to write_csv
  entries one-for-one, without merging by (project, description)
- Add `--raw` flag to the csv subparser; _cmd_csv branches on it
- Add TestToCsvEntries with 6 tests
- Update README with --raw usage example
- Add .coverage and htmlcov/ to .gitignore

tests/test_output.py

@@ -3,7 +3,7 @@ import io
 
 import pytest
 
-from timesheets.output import print_stories, print_summary, write_csv
+from timesheets.output import print_stories, print_summary, to_csv_entries, write_csv
 
 # ---------------------------------------------------------------------------
 # Shared fixtures
@@ -20,6 +20,64 @@ AGGREGATED = [
 ]
 
 
+# ---------------------------------------------------------------------------
+# to_csv_entries
+# ---------------------------------------------------------------------------
+
+
+def _raw_row(project, story, note, duration_hours):
+    return {
+        "project": project,
+        "story": story,
+        "story_raw": story,
+        "note": note,
+        "start": "09:00",
+        "end": "10:00" if duration_hours is not None else None,
+        "duration_hours": duration_hours,
+    }
+
+
+class TestToCsvEntries:
+    def test_basic_conversion(self):
+        rows = [_raw_row("bugs", "ticket 1", "", 1.0)]
+        assert to_csv_entries(rows) == [
+            {"project": "bugs", "description": "ticket 1", "quantity": 1.0}
+        ]
+
+    def test_skips_open_entries(self):
+        rows = [_raw_row("bugs", "ticket 1", "", None)]
+        assert to_csv_entries(rows) == []
+
+    def test_does_not_aggregate(self):
+        rows = [
+            _raw_row("bugs", "ticket 1", "", 0.5),
+            _raw_row("bugs", "ticket 1", "", 0.5),
+        ]
+        entries = to_csv_entries(rows)
+        assert len(entries) == 2
+        assert entries[0]["quantity"] == 0.5
+        assert entries[1]["quantity"] == 0.5
+
+    def test_description_combines_story_and_note(self):
+        rows = [_raw_row("bugs", "ticket 1", "fix", 1.0)]
+        assert to_csv_entries(rows)[0]["description"] == "ticket 1 - fix"
+
+    def test_project_stripped(self):
+        rows = [_raw_row("  bugs  ", "", "dsu", 0.25)]
+        assert to_csv_entries(rows)[0]["project"] == "bugs"
+
+    def test_mixed_open_and_closed(self):
+        rows = [
+            _raw_row("bugs", "ticket 1", "", 1.0),
+            _raw_row("bugs", "ticket 2", "", None),
+            _raw_row("scrum", "", "dsu", 0.25),
+        ]
+        entries = to_csv_entries(rows)
+        assert len(entries) == 2
+        assert entries[0]["description"] == "ticket 1"
+        assert entries[1]["description"] == "dsu"
+
+
 # ---------------------------------------------------------------------------
 # write_csv
 # ---------------------------------------------------------------------------