fix(command): refuse set-axis, set-page and siblings naming what the document lacks (improvise-31oe.2)

set-axis reads its axis at parse time, so an unknown keyword is an argument
error. set-axis, set-page, hide-item, show-item, toggle-group and switch-view
refuse an unknown category, item, group or view by name instead of doing
nothing, so a headless run exits non-zero.

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

tests/headless_cli.rs

@@ -121,6 +121,58 @@ fn a_parse_error_still_exits_non_zero() {
     );
 }
 
+/// improvise-31oe.2 at the process boundary, with a control that exits 0.
+/// Evidence: `context/test-evidence/cli.md`.
+#[test]
+fn an_unknown_category_axis_or_item_exits_non_zero_and_names_it() {
+    let scratch = Scratch::new("unknown_names");
+    let doc = seeded(&scratch, "m.improv");
+    let out = run_cmd(&["add-item Region East"], &doc);
+    assert!(out.status.success(), "the seed item: {}", stderr_of(&out));
+    for (line, missing) in [
+        ("set-axis Regoin row", "Regoin"),
+        ("set-page Region Nowhere", "Nowhere"),
+        ("set-axis Region sideways", "sideways"),
+    ] {
+        let out = run_cmd(&[line], &doc);
+        let said = stderr_of(&out);
+        assert!(!out.status.success(), "`{line}` exited 0; stderr={said:?}");
+        assert!(
+            said.contains(missing),
+            "`{line}` did not name {missing}: {said:?}"
+        );
+    }
+    let out = run_cmd(&["set-page Region East"], &doc);
+    assert!(out.status.success(), "the control: {}", stderr_of(&out));
+}
+
+/// improvise-31oe.3: one pipe-quoted argument, and a surplus one refused.
+/// Evidence: `context/test-evidence/cli.md`.
+#[test]
+fn a_pipe_quoted_name_reaches_the_document_whole() {
+    let scratch = Scratch::new("pipes");
+    let doc = seeded(&scratch, "m.improv");
+    let out = run_cmd(&["create-view |By area|"], &doc);
+    assert!(out.status.success(), "{}", stderr_of(&out));
+    let text = std::fs::read_to_string(&doc).expect("the document");
+    assert!(text.contains("## View: By area\n"), "{text}");
+    assert!(
+        !text.contains("|By"),
+        "a pipe reached the view name: {text}"
+    );
+
+    let out = run_cmd(&["create-view By area"], &doc);
+    let said = stderr_of(&out);
+    assert!(
+        !out.status.success(),
+        "a surplus argument exited 0: {said:?}"
+    );
+    assert!(
+        said.contains("\"area\""),
+        "the refusal does not name it: {said:?}"
+    );
+}
+
 /// Diagnostics go to stderr so that stdout stays free for a data output, and
 /// so `2>/dev/null` is the whole suppression story. `context/code/cli.md`.
 #[test]