Matrix: pin natural candidate ordering

8 tests covering completion-candidate order: connective keywords in
reading order (`to`/`from`/`in` before `table`), and command-part
keywords before schema identifiers. The ordering already held via
declaration-order preservation + keywords-first sectioning in
candidates_at_cursor; nothing pinned it until now, so a future
grammar or sort change could silently break the hint panel's
left-to-right reading.

tests/typing_surface/candidate_ordering.rs

@@ -0,0 +1,129 @@
+//! Matrix coverage for completion-candidate *ordering*.
+//!
+//! The order candidates appear in is load-bearing for the hint
+//! panel: it reads left-to-right, so the sequence must match
+//! how the command is spoken. Two invariants the user called
+//! out (handoff-14 ranker discussion):
+//!
+//! 1. Connective keywords appear in grammar-declaration / reading
+//!    order — `to` before `table` so `add column to table T`
+//!    reads correctly, never the jarring `table` / `to`.
+//! 2. Command-part keywords appear before schema identifiers
+//!    (table / column names) — grammar parts are read before
+//!    the content that fills them.
+//!
+//! These hold today via declaration-order preservation +
+//! keywords-first sectioning in `candidates_at_cursor`. Nothing
+//! pinned them until now, so a future grammar/sort change could
+//! silently break the reading order.
+
+use crate::typing_surface::*;
+
+/// Index of `needle` in the ordered completion candidate list,
+/// or panic with the full list for diagnosis.
+fn pos(a: &Assessment, needle: &str) -> usize {
+    let cands = completion_candidate_texts(a);
+    cands
+        .iter()
+        .position(|c| c == needle)
+        .unwrap_or_else(|| panic!("{needle:?} not in candidates: {cands:?}"))
+}
+
+/// Assert `first` appears before `second` in the candidate list.
+fn assert_before(a: &Assessment, first: &str, second: &str) {
+    let pf = pos(a, first);
+    let ps = pos(a, second);
+    assert!(
+        pf < ps,
+        "expected {first:?} (idx {pf}) before {second:?} (idx {ps}): {:?}",
+        completion_candidate_texts(a),
+    );
+}
+
+// =========================================================
+// Connective ordering: the `[connective] [table] <T>` shape
+// shared by the DDL commands.
+// =========================================================
+
+#[test]
+fn add_column_lists_to_before_table() {
+    let schema = schema_multi_table();
+    let a = assess_at_end("add column ", &schema);
+    assert_before(&a, "to", "table");
+    crate::snap!("add_column_connectives", a);
+}
+
+#[test]
+fn drop_column_lists_from_before_table() {
+    let schema = schema_multi_table();
+    let a = assess_at_end("drop column ", &schema);
+    assert_before(&a, "from", "table");
+    crate::snap!("drop_column_connectives", a);
+}
+
+#[test]
+fn rename_column_lists_in_before_table() {
+    let schema = schema_multi_table();
+    let a = assess_at_end("rename column ", &schema);
+    assert_before(&a, "in", "table");
+    crate::snap!("rename_column_connectives", a);
+}
+
+#[test]
+fn change_column_lists_in_before_table() {
+    let schema = schema_multi_table();
+    let a = assess_at_end("change column ", &schema);
+    assert_before(&a, "in", "table");
+    crate::snap!("change_column_connectives", a);
+}
+
+// =========================================================
+// Keywords-before-identifiers: at a position where both a
+// connective keyword and schema table names are valid, the
+// keyword comes first.
+// =========================================================
+
+#[test]
+fn add_column_keyword_precedes_table_identifiers() {
+    let schema = schema_multi_table();
+    let a = assess_at_end("add column ", &schema);
+    // `to` / `table` are command parts; Customers / Orders are
+    // schema identifiers — every keyword precedes every ident.
+    assert_before(&a, "table", "Customers");
+    assert_before(&a, "to", "Customers");
+    assert_before(&a, "to", "Orders");
+    crate::snap!("add_column_keyword_then_idents", a);
+}
+
+#[test]
+fn drop_column_keyword_precedes_table_identifiers() {
+    let schema = schema_multi_table();
+    let a = assess_at_end("drop column ", &schema);
+    assert_before(&a, "table", "Customers");
+    assert_before(&a, "from", "Orders");
+    crate::snap!("drop_column_keyword_then_idents", a);
+}
+
+#[test]
+fn insert_into_table_keyword_precedes_nothing_when_only_idents() {
+    // Sanity: at `insert into ` only table identifiers are
+    // valid — no keyword to precede them, but the ordering must
+    // still be deterministic (alphabetical among idents).
+    let schema = schema_multi_table();
+    let a = assess_at_end("insert into ", &schema);
+    assert_before(&a, "Customers", "Orders");
+    crate::snap!("insert_into_idents_only", a);
+}
+
+// =========================================================
+// After consuming the first connective, the second still
+// surfaces ahead of identifiers.
+// =========================================================
+
+#[test]
+fn add_column_after_to_lists_table_before_identifiers() {
+    let schema = schema_multi_table();
+    let a = assess_at_end("add column to ", &schema);
+    assert_before(&a, "table", "Customers");
+    crate::snap!("add_column_after_to", a);
+}