feat(import): a date column imports as one hierarchical category, the flat split a choice (improvise-8jk6.3)

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VdfEGXA7aJ6ftMsCc9PJze

tests/headless_cli.rs

@@ -612,3 +612,56 @@ fn a_headless_import_keeps_duplicates_separate_when_told_to() {
     assert!(doc.contains("= 10") && doc.contains("= 20"), "{doc}");
     assert!(!doc.contains("= 30"), "{doc}");
 }
+
+/// Dates across two years, one per month, so nothing collides.
+fn dated_csv(scratch: &Scratch) -> PathBuf {
+    let csv = scratch.path("dated.csv");
+    std::fs::write(
+        &csv,
+        "Date,Revenue\n2024-01-15,1\n2024-04-02,10\n2025-01-03,100\n",
+    )
+    .unwrap();
+    csv
+}
+
+/// improvise-8jk6.3, headless: `--extract` builds ONE hierarchical category by
+/// default, as the wizard does, and it is written with its `>` lines.
+#[test]
+fn a_headless_date_import_is_one_hierarchical_category() {
+    let scratch = Scratch::new("date_hierarchy");
+    let out_path = scratch.path("out.improv");
+    let out = run_import(
+        &dated_csv(&scratch),
+        &out_path,
+        &[
+            "--extract",
+            "Date:Year",
+            "--extract",
+            "Date:Quarter",
+            "--extract",
+            "Date:Month",
+        ],
+    );
+    assert!(out.status.success(), "{}", stderr_of(&out));
+    let doc = std::fs::read_to_string(&out_path).unwrap();
+    assert!(!doc.contains("Date_Month"), "{doc}");
+    assert!(doc.contains("- |2024-01|[|2024-Q1|]"), "{doc}");
+    assert!(doc.contains("> |2024-Q1|[|2024|]"), "{doc}");
+    assert!(!doc.contains("expanded"), "it opens folded: {doc}");
+}
+
+/// The flat split stays available headless, as `s` makes it in the wizard.
+#[test]
+fn a_headless_date_import_splits_when_told_to() {
+    let scratch = Scratch::new("date_split");
+    let out_path = scratch.path("out.improv");
+    let out = run_import(
+        &dated_csv(&scratch),
+        &out_path,
+        &["--extract", "Date:Month", "--split-date", "Date"],
+    );
+    assert!(out.status.success(), "{}", stderr_of(&out));
+    let doc = std::fs::read_to_string(&out_path).unwrap();
+    assert!(doc.contains("## Category: Date_Month"), "{doc}");
+    assert!(doc.contains("2024-01-15"), "the raw dates stay: {doc}");
+}