Add env flag TEMPORARY_TABLES=true|false to switch temp vs permanent tables

[simbo1905]

Proposal: introduce an environment variable TEMPORARY_TABLES to control whether generated SQL uses CREATE OR REPLACE TEMPORARY TABLE or CREATE OR REPLACE TABLE for before_table, after_table, and diff_result.

Context:

• Burner/demo accounts don’t need session-scoped temp tables; permanent is simpler for multi-command runs.
• Some workflows (e.g., copy-paste into Web UI) may still prefer TEMP tables.

Scope:

• Template: parameterize the diff_result creation to include TEMPORARY when the flag is true.
• Samples/README: document the flag and show both modes.
• Tests: ensure behavior is unchanged in default mode; optionally add a paramized test for the TEMPORARY variant.

Defaults:

• Suggest default TEMPORARY_TABLES=false for demo flows; allow override via env and (optionally) a CLI flag.