fix(pool): discard connection on error 1290 (Aurora read-only failure)

[natetarrh]

Problem

During an Aurora MySQL failover, an existing writable connection becomes read-only. Subsequent writes return error 1290 (ER_OPTION_PREVENTS_STATEMENT):

The MySQL server is running with the --read-only option so it cannot execute this statement

The pool returns this stale read-only connection to the free list, so all subsequent callers receive the same broken connection.

Fixes #2050

Prior Art

The Go MySQL driver handles this same scenario by closing the connection and returning ErrBadConn when it encounters errors 1290, 1792, or 1836 during failover. This causes Go's database/sql pool to discard the connection and create a new one:

https://github.com/go-sql-driver/mysql/blob/76c00e35a8d48f8f70f0e7dffe584692bd3fa612/packets.go#L599-L612

Fix

pool.query() and pool.execute() now detect error 1290 and call conn.destroy() instead of conn.release(), forcing the pool to create a fresh connection for the next caller.

Test

Adds an integration test (test-aurora-failover-readonly.test.cjs) that simulates the failover using a mock server:

1. Pool gets a connection, first query succeeds
2. Mock server starts returning error 1290 (simulating failover)
3. Asserts the pool discards the bad connection and provides a new one (different threadId)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.94%. Comparing base (b0f8a77) to head (379139b).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4075      +/-   ##
==========================================
+ Coverage   89.87%   89.94%   +0.07%     
==========================================
  Files          86       86              
  Lines       13624    13651      +27     
  Branches     1619     1629      +10     
==========================================
+ Hits        12244    12279      +35     
+ Misses       1380     1372       -8     

Flag	Coverage Δ
compression-0	89.06% <100.00%> (+0.08%)	⬆️
compression-1	89.92% <100.00%> (+0.07%)	⬆️
static-parser-0	87.53% <100.00%> (+0.08%)	⬆️
static-parser-1	88.29% <100.00%> (+0.08%)	⬆️
tls-0	89.35% <100.00%> (+0.07%)	⬆️
tls-1	89.72% <100.00%> (+0.07%)	⬆️

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