fix(plugin-snowflake): decode the wire encodings the query-request endpoint sends

[yankewei]

Snowflake driver fixes, five commits, each reviewed and merged on its own before landing here: #2467, #2468, #2469, #2470, plus the original decoding change.

The reported bug

SnowflakeConnection.box is type blind. The legacy /queries/v1/query-request endpoint sends every cell as a JSON string in Snowflake's own internal encoding, and the driver never consulted the rowtype metadata it had already parsed, so a DATE reached the app as 20682 rather than 2026-08-17.

That one boxing produced all three reported symptoms, because display, the picker seed and the UPDATE / DELETE WHERE anchor all read the same PluginCellValue.

Two corrections to the original approach

DATE_OUTPUT_FORMAT cannot work, so it is dropped. Its default is already YYYY-MM-DD and the wire still carries 20682. Snowflake's own converter_snowsql.py reads the parameter and still calls time.gmtime(int(value) * 86400) first; gosnowflake and snowflake-jdbc decode epoch days unconditionally. It is a display parameter for text casts, not a wire format switch.

Foundation is the wrong calendar. Snowflake documents that it does not adjust dates before 1582 to match the Julian calendar. Measured on this toolchain, Calendar(identifier: .gregorian), Calendar(identifier: .iso8601), ISO8601DateFormatter, Date.FormatStyle.iso8601 and a POSIX DateFormatter all render epoch day -719162 as 0001-01-03 where Snowflake means 0001-01-01, and gregorianStartDate does not exist in the macOS SDK. The conversion is integer arithmetic, and testProlepticGregorian fails the moment anyone reimplements it on Foundation.

What is in here

Type	Wire	Was	Now
DATE	days since epoch	20682	2026-08-17
TIME	seconds since midnight	3600.000000000	01:00:00
TIMESTAMP_NTZ	seconds since epoch	1755388800.000000000	2025-08-17 00:00:00
TIMESTAMP_LTZ	seconds since epoch	1755388800.000000000	2025-08-17 00:00:00Z
TIMESTAMP_TZ	seconds, offset + 1440	1616173619.000000000 1500	2021-03-19 18:06:59+01:00
BINARY	hex string	0x34383635364336433646	the bytes themselves

Plus, from the stacked reviews:

• One SQL escaper (fix(plugin-snowflake): give every statement builder one SQL escaper #2467). SnowflakeObjectQueries.escapeLiteral doubled the quote and left the backslash, so a schema named x\' OR 1=1 -- closed the literal and ran its own SQL. Three copies of the escaper and five of the identifier quoter existed and nothing made them agree; there is now one owner and no hand-rolled escaping anywhere else in the plugin.
• Offsets the parser cannot represent (fix(plugin-snowflake): keep a timestamp offset the date parser cannot represent as text #2468). TimeZone(secondsFromGMT:) is nil past eighteen hours and the shared parser reads that nil as GMT, so a +18:30 payload moved the instant by eighteen and a half hours. Such a value keeps its raw text.
• Affected row counts (fix(plugin-snowflake): take the affected row count from the statement type, not a column name #2469). The count was read off a column named number of rows, which missed UPDATE and MERGE entirely and reported a SELECT COUNT(*) AS "number of rows" as rows changed. It now comes from the response's statementTypeId.
• Session identity (fix(plugin-snowflake): key the shared session on the saved connection and scope Stop to its own driver #2470). The shared session was keyed on the account, so two saved connections to one account shared a session and USE DATABASE in one window moved the other. Stop also aborted every query on the session, including a sidebar refresh beside it.

A value that cannot be decoded is never invented

Every arm returns the raw text unchanged when the encoding does not explain the value: a non-integer, an out of range epoch day, a malformed offset, an odd-length hex string. Decoding is keyed on the column, never on the value, so an integer sitting in a VARCHAR is left alone.

The picker

A date control cannot say "I could not read this": NSDatePicker.dateValue and every SwiftUI DatePicker binding are a non-optional Date. A date cell whose text is non-empty and does not parse now opens the existing text editor instead of a picker seeded with today.

Tests

63 cases across SnowflakeValueDecoderTests, SnowflakeSQLTests, SnowflakeStatementTypeTests, SnowflakeSessionKeyTests and SnowflakeTypeMapperTests. Decoder expectations were computed independently in Python's proleptic Gregorian calendar rather than from the implementation.

Verified on the merged branch: build PASS, SwiftLint 0 violations, AllPlugins compiles SnowflakeDriverPlugin clean, docs checks PASS.

Not fixed here

Version 0 TIMESTAMP_TZ payloads pack the zone into the low bits of a single number instead of the "<epoch> <offset>" pair. Decoding it needs Snowflake's timezone index table, which cannot be verified without an account, so those values fall through to raw text, which is the behaviour before this change.

Fixes #2454

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