docs: fix stale put(String) builder signature in reference

The Chunk builder row still read put(String column, Object data) but
the method has taken ColumnName since #200. A survey of backticked
method-signature claims (prompted by the #202 review) surfaced it;
#202 fixed the fenced .put snippets but missed this reference table row.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: dfa1

docs/reference.md

@@ -108,7 +108,7 @@ at the call site.
 
 | Method                          | Notes                                                              |
 |---------------------------------|--------------------------------------------------------------------|
-| `put(String column, Object data)` | Adds one column; returns `this` for chaining                       |
+| `put(ColumnName column, Object data)` | Adds one column; returns `this` for chaining                   |
 
 Accepted array types per column `DType`: