fix: cast numeric FORMAT arguments for DuckDB

[weicao]

Scope

Fix MySQL FORMAT(x, d[, locale]) when x is an integer. DuckDB rejects precision format specifiers for integer arguments, while MySQL accepts them. The translator now casts the value to DOUBLE before formatting.

Evidence

• Base exact main: 749b616
• Baseline: integer FORMAT subtests fail with precision not allowed for this argument type.
• Patched: 4 FORMAT TestQueriesSimple subtests pass, including da_DK locale variants.
• go test ./transpiler passes.
• No JSON, HAVING, dependency, image, or version changes.

Please platform-sign the replacement head before review. Do not merge or change release tags from this PR.

[leon-ape]

Independent review of exact platform-signed head e5b396c.

• GitHub web-flow verified; unique parent is exact main 749b616; tree ae59af41133032963be2e93a1c62c0fd9e401073.
• Scope is exactly three files: transpiler/translate.go, transpiler/translate_test.go, format_precision_test.go.
• go test ./transpiler -count=3 passed.
• Four TestQueriesSimple FORMAT cases passed 3 consecutive runs.
• TestFormatPreservesNumericPrecision passed 3 consecutive runs, including 9007199254740993 and 30-digit DECIMAL. Additional negative DECIMAL, locale, string, NULL, and dynamic-digit probes passed.
• Parent/head TestQueriesSimple comparison removed only the two intended integer FORMAT failures and introduced no new failure.

The remaining Go/binlog/Postgres CI failures match known parent baseline differences outside these files. No merge or image action performed.