fix(plugins): MySQL numeric column rendering and Query cancelled alert race

[datlechin]

Summary

Two regressions from #1190 (refactor(plugins)!: typed PluginCellValue for binary cells):

1. MySQL numeric / date columns render as hex bytes

INT 1 displayed as 0x31, DECIMAL 12.50 as 0x31322E3530, dates as raw byte sequences. The new binary-routing predicate was field.charsetnr == 63, but MariaDB reports charset 63 for every non-character type, not just BLOB/VARBINARY.

Fix: MariaDBFieldClassifier.isBinary(typeRaw:charset:) now requires both charset 63 AND a BLOB / VARBINARY / BIT field type. Numerics, decimals, dates, JSON, ENUM, SET, GEOMETRY all route to .text as they should.

Audited every plugin touched by #1190; MySQL is the only one with this bug. PostgreSQL (OID 17), DuckDB (DUCKDB_TYPE_BLOB), MSSQL (SYBBINARY|SYBVARBINARY|SYBIMAGE), Oracle (.raw|.longRAW|.blob), Cassandra (CASS_VALUE_TYPE_BLOB), BigQuery (schema type "BYTES"), MongoDB (as? Data), DynamoDB (.binary enum) all use sound predicates. ClickHouse, Redis, CloudflareD1, Etcd, LibSQL never emit .bytes on result rows.

2. "Query Execution Failed: Query cancelled" alert race

When opening a table tab, the in-flight query is sometimes cancelled by supersession (refresh, preview-tab promotion, teardown). The plugin threw a custom error with message "Query cancelled", which the catch path in MainContentCoordinator / QueryExecutionCoordinator+Parameters / +MultiStatement surfaced as a user alert because there was no Task.isCancelled / cancellation-error filter.

Fix:

• MySQL, MSSQL, and MongoDB drivers now throw the standard CancellationError() instead of a custom *Error("Query cancelled"). This aligns with what the streaming paths already do (Oracle, DuckDB, the streaming branches of those same drivers).
• All three catch sites (MainContentCoordinator:1107-1119, +Parameters:156-168, +MultiStatement:140-156) now short-circuit when error is CancellationError || Task.isCancelled. Cleanup state mutations still run; only the alert is suppressed.

Test plan

• Build and open MySQL connection. Click order_items (1M rows seeded). INT and DECIMAL render as 1, 12.50 etc. — no 0x... hex.
• Click between tables rapidly to trigger query supersession. No "Query cancelled" alert should appear.
• Hit Refresh while a query is loading. No alert.
• Close a connection mid-query. No alert.
• MariaDBFieldClassifierTests — 7 new tests covering BIT, BLOB family, VAR_STRING/STRING charset 63, numerics, temporals, JSON/ENUM/SET/GEOMETRY. Verified via xcodebuild test -only-testing:TableProTests/MariaDBFieldClassifierTests → ** TEST SUCCEEDED **.