feat(duckdb)!: support transpilation of ARRAY_REMOVE_AT

[fivetran-MichaelLee]

Implements transpilation of Snowflake's ARRAY_REMOVE_AT(array, position) to DuckDB using LIST_CONCAT and array slicing.

Transpilation patterns

• Position 0: arr[2:]
• Positive position: LIST_CONCAT(arr[1:p], arr[p+2:])
• Position -1: arr[1:LEN(arr)-1]
• Negative position: LIST_CONCAT(arr[1:LEN(arr)+p], arr[LEN(arr)+p+2:])

All expressions wrapped in CASE WHEN arr IS NULL THEN NULL ELSE ... END for proper NULL propagation.

Limitations

• Only supports literal integer positions
• Non-literal positions remain untranspiled with unsupported warning

Changes

• Added ArrayRemoveAt expression class
• Implemented _array_remove_at_sql in DuckDB generator
• Added test cases covering positive/negative positions, edge cases, and non-literal handling

[github-actions]

SQLGlot Integration Test Results

Comparing:

• this branch (sqlglot:mlee/transpile-array_remove_at, sqlglot version: mlee/transpile-array_remove_at)
• baseline (main, sqlglot version: 28.7.1.dev13)

⚠️ Limited to dialects: bigquery, snowflake, duckdb

By Dialect

dialect	main	sqlglot:mlee/transpile-array_remove_at	difference	links
bigquery -> bigquery	2592/2624 passed (98.8%)	2592/2624 passed (98.8%)	No change	full result / delta
bigquery -> duckdb	1846/2623 passed (70.4%)	1846/2623 passed (70.4%)	No change	full result / delta
duckdb -> duckdb	4003/4003 passed (100.0%)	4003/4003 passed (100.0%)	No change	full result / delta
snowflake -> duckdb	1313/2623 passed (50.1%)	1317/2623 passed (50.2%)	⬆ improved by 0.2%	full result / delta
snowflake -> snowflake	2607/2623 passed (99.4%)	2606/2623 passed (99.4%)	No change	full result / delta

Overall

main: 14496 total, 12361 passed (pass rate: 85.3%), sqlglot version: 28.7.1.dev13

sqlglot:mlee/transpile-array_remove_at: 14496 total, 12364 passed (pass rate: 85.3%), sqlglot version: mlee/transpile-array_remove_at

Difference: No change