docs: clarify Claro v1 status and validation

docs/ADVANCED_STATIC_TYPING.md

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+# Advanced Static Typing
+
+Claro v1.18.26 adds the first advanced static-typing foundation: typed containers checked by `claro typecheck`.
+
+## Typed lists
+
+```claro
+SET names AS LIST OF TEXT TO LIST
+ADD "Ada" TO names
+ADD "Grace" TO names
+```
+
+The type checker now rejects wrong item types:
+
+```claro
+SET names AS LIST OF TEXT TO LIST
+ADD 123 TO names
+```
+
+Output:
+
+```text
+Type mismatch for list names: expected TEXT item, but this value looks like NUMBER.
+```
+
+## Typed maps
+
+```claro
+SET scores AS MAP OF NUMBER TO MAP
+PUT scores KEY "math" VALUE 98
+```
+
+The type checker rejects wrong value types:
+
+```claro
+SET scores AS MAP OF NUMBER TO MAP
+PUT scores KEY "oops" VALUE "high"
+```
+
+Output:
+
+```text
+Type mismatch for map scores: expected NUMBER value, but this value looks like TEXT.
+```
+
+## Status
+
+This is currently a static checker feature. It improves `claro typecheck` and validation confidence. Runtime enforcement for every container mutation can be added later after the syntax is classroom-tested.