Update release notes for v25.4-v25.4.0-rc.1

Author: Automated Release Bot

src/current/_includes/releases/v25.4/v25.4.0-rc.1.md

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+## v25.4.0-rc.1
+
+Release Date: October 22, 2025
+
+{% include releases/new-release-downloads-docker-image.md release=include.release %}
+
+<h3 id="v25-4-0-rc-1-sql-language-changes">SQL language changes</h3>
+
+- Changes scan misestimate logging gated behind
+  `sql.log.scan_row_count_misestimate.enabled` to use structured logging
+  including the table and index being scanned, the estimated and actual
+  row counts, the time since the last table stats collection, and the
+  table's estimated staleness. [#155123][#155123]
+- Added a default-off cluster setting
+  (`sql.log.scan_row_count_misestimate.enabled`) that enables logging a
+  warning on the gateway node when optimizer estimates for scans are
+  inaccurate. The log message includes the table and index being scanned,
+  the estimated and actual row counts, the time since the last table stats
+  collection, and the table's estimated staleness. [#155123][#155123]
+- Added the `INSPECT` command, which runs consistency validation check jobs against tables or databases and specified indexes. [#155441][#155441]
+- Added the
+  bulkio.index_backfill.vector_merge_batch_size cluster setting to control
+  how many vectors to merge into a vector index per transaction during
+  create operations. By default, this defaults to 3. [#155509][#155509]
+- Vector indexing is now enabled by default. [#155561][#155561]
+
+<h3 id="v25-4-0-rc-1-bug-fixes">Bug fixes</h3>
+
+- Fixed a bug that caused internal errors for `INSERT .. ON CONFLICT .. DO UPDATE` statements when the target table had both a computed column and a `BEFORE` trigger. This bug was present since triggers were introduced in v24.3.0. [#155077][#155077]
+- Disable a feature
+  (kv.lock_table.unreplicated_lock_reliability.split.enabled) that could
+  lead to a node crash. [#155366][#155366]
+- Previously, we could corrupt the first bucket of
+  table statistic histograms in certain cases, causing underestimates for
+  range counts near the lower end of the domain, which is now fixed. [#155415][#155415]
+- A potential deadlock during vector index
+  creation has been corrected. [#155508][#155508]
+- Added proper dependency handling when adding a constraint with `NOT VALID` that references a user-defined function (UDF). [#155528][#155528]
+
+
+[#155441]: https://github.com/cockroachdb/cockroach/pull/155441
+[#155561]: https://github.com/cockroachdb/cockroach/pull/155561
+[#155366]: https://github.com/cockroachdb/cockroach/pull/155366
+[#155415]: https://github.com/cockroachdb/cockroach/pull/155415
+[#155508]: https://github.com/cockroachdb/cockroach/pull/155508
+[#155123]: https://github.com/cockroachdb/cockroach/pull/155123
+[#155509]: https://github.com/cockroachdb/cockroach/pull/155509
+[#155077]: https://github.com/cockroachdb/cockroach/pull/155077
+[#155528]: https://github.com/cockroachdb/cockroach/pull/155528