fix(sql): attach dialect-default temporal fsp when catalogs omit it

[cursor]

Bug and impact

Cross-dialect migrate to MySQL/MariaDB still truncated fractional seconds when the source type string omitted precision — the common case for Postgres timestamp / timestamptz / time (format_type drops (6) for the default typmod), bare Oracle TIMESTAMP, and SQL Server datetime / default datetime2.

Concrete trigger: Postgres column created_at timestamp storing 12:00:00.123456 → migrate to MySQL created bare datetime (= fsp 0) → value became 12:00:00.

Root cause

PR #286 preserved explicit fsp in shapeCanonical, but catalogs often omit the parenthetical when the engine default applies. Parse left length unset; MySQL render then emitted bare datetime/time.

Fix

• withDefaultTemporalFsp helper
• Postgres / Redshift / DuckDB / Oracle / Db2: bare temporal → default fsp 6 (Db2: TIMESTAMP only)
• SQL Server: datetime→3, smalldatetime→0, bare datetime2/time/datetimeoffset→7
• MySQL bare datetime stays fsp 0 (correct for that engine)

Validation

• npx vitest run packages/sql/src/modules/type-mapping.test.ts — 18 passed
• npx vitest run packages/sql — 736 passed, 2 expected fail

  

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Note

Medium Risk
Changes how temporal types are parsed and rendered across dialects, which can alter generated DDL and data precision on migrate. Defaults are engine-correct but any mismatch would still truncate or widen fractional seconds.

Overview
Stops cross-dialect migrate from silently dropping fractional seconds when the source catalog omits precision (Postgres format_type bare timestamp, Oracle TIMESTAMP, SQL Server datetime / default datetime2). Those used to render as MySQL datetime (fsp 0).

Adds withDefaultTemporalFsp and applies engine defaults on parse: 6 for Postgres, Redshift, DuckDB, Oracle, and Db2 TIMESTAMP; SQL Server datetime→3, smalldatetime→0, bare datetime2/time/datetimeoffset→7. MySQL bare datetime stays unsized (true fsp 0).

canonicalEquals now treats Postgres timestamp as timestamp(6).

^{Reviewed by Cursor Bugbot for commit c010d58. Bugbot is set up for automated code reviews on this repo. Configure here.}

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