tool run: read-only DuckDB statements are refused as writes, and the refusal names an internal permission #1648

Found during the v0.12.9 release review (#1647).

• SUMMARIZE t and CALL pragma_version() on DuckDB are refused without --allow-write, although they only read.
• The refusal reads Permission denied: sql_execute_write. Re-run with --allow-write to enable writes. It names an internal permission kind, not the statement, so a user cannot tell what was read as a write. The only way past it is --allow-write, which enables every write.
• Multi-statement reads are refused ("Run each read separately"), while --allow-write accepts several statements in one call. The docs don't say so.

Suggested: name the statement kind in the refusal, treat known read-only DuckDB statements as reads, and document the multi-statement difference.

Deferred because it changes the classifier, which is being hardened separately in #1644.