test: add COPY INTO, LATERAL FLATTEN, and additional Snowflake dialect test coverage

[elipollak]

Summary

Follow-up to #170 — adds test coverage for Snowflake-specific syntax that isn't covered by the existing tests:

• COPY INTO — verifies it parses as Copy, not Unknown (the original issue in COPY statements incorrectly classified as "Unknown" instead of "Copy" #161)
• LATERAL FLATTEN with colon-path extraction
• Nested dot-path notation (data:user.address.city::STRING)
• Bracket notation (data['key'])
• OBJECT_CONSTRUCT, GET_PATH functions

Also adds Copy to the sql_statement_permissions example in the README so users know they can configure it explicitly.

Test plan

• Existing tests continue to pass
• New TestSnowflakeSpecificSyntax class passes (7 parametrized + 1 COPY INTO)

🤖 Generated with Claude Code

[bccolema]

Oooo, would this also separate SHOW out to its own setting option instead of bucketing it under command?!! If so, PLEASE APPROVE

[arborluke]

Ah I think I have duplicated this PR ! We came to the same conclusion! #179

[sfc-gh-twhite]

This should now be resolved with the merging of #170 - I do like these tests a lot though! Would you want to rebase and add these tests to cover statements like COPY?

We should also add an explicit example of this in the README as well.

mcp/README.md

Lines 74 to 81 in f74d74f

	sql_statement_permissions: # List SQL statements to explicitly allow (True) or disallow (False).
	# - All: True # To allow everything, uncomment and set All: True.
	- Alter: True
	- Command: True
	- Comment: True
	- Commit: True
	- Create: True
	- Delete: True

[elipollak]

Sounds good @sfc-gh-twhite I rebased and updated the PR with the additional test coverage (COPY INTO, LATERAL FLATTEN, nested dot-path, bracket notation, OBJECT_CONSTRUCT, GET_PATH) and added Copy in the README permissions example.

[sfc-gh-twhite]

Thanks for the submission! Appreciate you rebasing after #170 to include your test for COPY INTO.