walker: flag LIKE on a numeric column (ADR-0027 Amendment 1)

LIKE is a text-pattern match; against a numeric column (int,
real, decimal, serial) it runs but is almost never intended.
predicate_warnings now emits a WARNING for it, spanned at the
target column. New Type::is_numeric; catalog key
diagnostic.like_numeric; ADR-0027 gains "Amendment 1" and the
adr/README index line is updated per the index-upkeep rule.

bool and the text-/blob-backed types are deliberately not
flagged — see the amendment for the rationale.

3 walker tests (int, decimal NOT LIKE, text-column clean).
1108 passing, clippy clean.

src/dsl/types.rs

@@ -101,6 +101,18 @@ impl Type {
         ]
     }
 
+    /// True for the numeric types — `int`, `real`, `decimal`,
+    /// `serial`. `bool` (stored 0/1) and the text- / blob-backed
+    /// types are not numeric. Used to flag a `LIKE` text-pattern
+    /// match against a numeric column (ADR-0027, Amendment 1).
+    #[must_use]
+    pub const fn is_numeric(self) -> bool {
+        matches!(
+            self,
+            Self::Int | Self::Real | Self::Decimal | Self::Serial
+        )
+    }
+
     /// The user-facing type that an FK column should use to
     /// reference a primary key of *this* type. For most types
     /// the answer is the same type; for `serial` and `shortid`