constraints: CHECK-violation friendly error + typing-surface matrix (ADR-0029 §10)

Completes ADR-0029's implementation: the friendly-error layer
now names the rule a CHECK violation broke, and the
typing-surface matrix covers the whole constraint grammar.

CHECK-violation friendly error (ADR-0029 §10):
- enrich_dsl_failure gains a CHECK branch — it reads the column
  from the engine's `CHECK constraint failed: <column>`
  message, then resolves the table, the offending value, and
  the column's compiled CHECK expression.
- FailureContext / TranslateContext carry the resolved
  check_rule; translate_check renders "the value <v> breaks the
  rule `<rule>`" when it is known, falling back to the plain
  hint otherwise.

Typing-surface matrix: a new `constraints` submodule, 14 cells
covering the create-table / add-column constraint suffix and
the add-constraint / drop-constraint commands (174 → 188).

16 tests added (1 translate unit, 1 enrichment integration, 14
matrix cells).

src/friendly/strings/en-US.yaml

@@ -85,17 +85,20 @@ error:
       headline: "`{table}.{column}` cannot be null."
       hint: "The `{column}` column is required — pick a non-null value, or do not include `{column}` in your `set` list."
 
-  # CHECK constraint violations. Placeholder coverage —
-  # the playground does not emit CHECK constraints today
-  # (track C3), but the catalog is wired so the wording
-  # is ready when constraint-management lands.
+  # CHECK constraint violations (ADR-0029 §10). When the
+  # runtime resolves the column's compiled CHECK expression,
+  # `hint_with_rule` names both the offending value and the
+  # rule; the plain `hint` is the fallback when enrichment
+  # could not resolve the rule.
   check:
     insert:
       headline: "check constraint refused `{table}.{column}`."
       hint: "A check constraint requires `{column}` to satisfy a rule the inserted value did not."
+      hint_with_rule: "The value {value} breaks the rule `{rule}` — `{column}` must satisfy it."
     update:
       headline: "check constraint refused `{table}.{column}`."
       hint: "A check constraint requires `{column}` to satisfy a rule the new value did not."
+      hint_with_rule: "The new value {value} breaks the rule `{rule}` — `{column}` must satisfy it."
 
   # Type mismatch — engine-side STRICT refusal of a wrong-shape
   # value. Mostly the `change column ... --dont-convert` path