fix(postgres): return date/timestamp values verbatim instead of host-local Dates

[tianzhou]

Fixes #416

Problem

timestamp without time zone and date values from Postgres came back shifted by the DBHub host's UTC offset. pg-types parses these OIDs with the multi-argument Date constructor (host-local time), and the JSON serializer then renders the Date via toISOString(). On a host in America/Chicago, a stored 2026-01-01 12:00:00 was returned as 2026-01-01T18:00:00.000Z: the host offset baked in, a misleading Z suffix, and microseconds truncated. date was also affected (rendered as a shifted midnight instant). timestamptz was unaffected because pg-types takes the Date.UTC branch for it.

Reproduced locally against the installed pg with TZ=America/Chicago:

OID	Type	Input	Before
1114	timestamp	2026-01-01 12:00:00	2026-01-01T18:00:00.000Z
1082	date	2026-01-01	2026-01-01T06:00:00.000Z
1114	timestamp	2026-01-01 12:00:00.123456	2026-01-01T18:00:00.123Z

Fix

• New src/connectors/postgres/type-parsers.ts registers string passthrough parsers for date, timestamp, timestamptz and their array types.
• Wired in via PoolConfig.types, so it is scoped to DBHub's pool and does not mutate the process-wide pg.types registry.
• Values now render as the text psql would show, with microseconds preserved. timestamptz is included so the three date/time types render consistently and the session offset stays visible.
• Plain time (OID 1083) already came back as a string and is unchanged.

Tests

• src/connectors/__tests__/postgres-type-parsers.test.ts: unit tests for the parsers, including host-timezone independence, array types, delegation of other OIDs to pg-types, and no global mutation.
• src/connectors/__tests__/postgres.integration.test.ts: regression assertion against a real Postgres container.

Unit suite passes locally; the Postgres integration suite requires Docker and will run in CI.

🤖 Generated with Claude Code

https://claude.ai/code/session_01EL7QBrNvJJvVHaDvmC9MZL

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Generated by Claude Code

[Copilot]

🟢 Approval recommended

The change is scoped to the Postgres pool, matches the stated bug/acceptance criteria, and is covered by both unit and integration regression tests.

Pull request overview

This PR fixes Postgres date/time value rendering so date, timestamp, and timestamptz are returned as the server’s verbatim text (instead of host-local Date objects that get JSON-serialized with shifted/ambiguous UTC timestamps), addressing issue #416.

Changes:

• Adds a Postgres pool-scoped types configuration that passthrough-parses date/time OIDs (including array OIDs) as strings.
• Wires the custom type parsers into the Postgres connector via PoolConfig.types (avoiding process-wide pg.types mutation).
• Adds unit + integration regression tests covering microseconds, arrays, delegation for other OIDs, and no global mutation.

File summaries

File	Description
src/connectors/postgres/type-parsers.ts	Introduces pool-scoped type parsers to return date/timestamp/timestamptz (and arrays) as verbatim text.
src/connectors/postgres/index.ts	Applies the custom type parser config to the connector’s pool to avoid host-timezone shifts.
src/connectors/tests/postgres.integration.test.ts	Adds integration regression coverage ensuring executeSQL returns the expected verbatim strings.
src/connectors/tests/postgres-type-parsers.test.ts	Adds unit tests verifying passthrough behavior, delegation, timezone-independence, and no global mutation.

Review details

• Files reviewed: 4/4 changed files
• Comments generated: 0
• Review effort level: Lite

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