Release v1.26.5.2

Release candidate 1 for v1.26.5.2

docs(release): add release notes for v1.26.5.1

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs(release): update CHANGELOG and release notes for v1.26.5 final

- Correct release date to 2026-05-08 (RC3 signed off today)
- Add binlog WRITE_ROWS fix (FDE crash loop, KNNIndex coordinates,
  BUILD binlog position snapshot) to Fixed section

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

fix(component): fix binlog WRITE_ROWS handler for multi-column tables

Three bugs causing mc_test failure in smoke-component.sh:

1. FDE reconnect crash loop: MySQL 8.4/9.7 sends FORMAT_DESCRIPTION_EVENT
   (type=15) at reconnect with non-zero next_log_pos pointing past EOF.
   Skip currentBinlogPos update for FDE events.

2. KNNIndex missing binlog coordinate storage: set/getLastUpdateCoordinates
   were no-ops so isAfter() always returned true. Added m_binlogFile and
   m_binlogPosition with sentinel init in initIndex().

3. BUILD saves stale listener position: use SHOW BINARY LOG STATUS on the
   open BUILD connection instead of currentBinlogPos so the saved position
   covers all rows read during the build.

smoke-component.sh 8.4 and 9.7: all 15 checks PASS.
Extend mc_test sleep 6->12s and improve failure diagnostics.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Release candidate 2 for v1.26.5

Fixes over RC1:
- Fix GLIBCXX_3.4.30 ABI issue: plugin .so now static-links libstdc++/libgcc
  so it loads on OracleLinux 8 (mysql8.0 Docker image smoke was failing)
- Expand smoke-component.sh: cosine/IP distance, myvector_is_valid,
  index status, persist-and-reload, multi-column binlog test

Release candidate 1 for v1.26.5

Release v1.26.3

Release candidate 1 for v1.26.3

PR76 checkpoint: component migration 8.4-9.6, CI partial pass, 4 jobs…

… failing