docs: correct data workflows, SQL and operations (#4534)

This PR is part of the documentation revamp. Once the full set of PRs is
merged, we’ll publish the combined site to staging for review before
updating docs.lancedb.com.

The curation, SQL and operations pages contain outdated claims and
examples that do not reliably work as written.

This corrects those pages against the reviewed SDK and local server
evidence, including prepared statements, background jobs, cleanup and
monitoring. Integration guides are grouped with their examples in #4533.

Function and Secret-object documentation stays unpublished until its
release. The two Function pages are listed in `.mintignore` and left out
of the navigation, and the sections about them on other pages are MDX
comments.

Stacked on #4533. Each MDX file has one PR owner. Rebase onto main after
#4533 is squash-merged.

Local assembly, Mint validation and link checks pass, and the assembled
site shows no Function or Secret-object content. A local release
rehearsal that uncomments the drafts and restores the navigation also
passes. Hold publication until this PR and lancedb/sophon#8688 are on
`main`.

docs/web/sql/operators.mdx

@@ -6,10 +6,11 @@ icon: plus-minus
 keywords: ["operators", "literals", "precedence", "null", "cast", "interval"]
 ---
 
-<Badge color="red">Enterprise</Badge> [SQL runs on a deployment.](/sql)
+<Badge color="red">Enterprise</Badge> [SQL runs in LanceDB Enterprise.](/sql)
 
-The operator set is DataFusion's. This page covers what is worth knowing when
-the operands are Lance columns.
+LanceDB uses DataFusion's SQL operators. This page describes comparison,
+logical and arithmetic operators, literal values, type conversions and
+operator precedence.
 
 ## Comparison {#comparison}
 
@@ -44,8 +45,8 @@ IN`, which is the usual place this bites. See
 <Warning>
 Arithmetic over a vector column is **list** arithmetic, not scalar arithmetic —
 a vector is a `FixedSizeList<Float32>`. When the operation you want is a
-similarity comparison, use [vector search](/search/vector-search); there is no
-SQL form for it.
+similarity comparison, use [vector search](/search/vector-search); whether SQL
+can express it [depends on the Enterprise server version](/basics/sql#no-vector-sql).
 </Warning>
 
 ## Literals {#literals}
@@ -66,10 +67,13 @@ or a name with mixed case: `SELECT "order" FROM "MyTable"`.
 ## Casting {#casting}
 
 ```sql
-SELECT CAST(identifier AS VARCHAR), identifier::VARCHAR FROM documents
+SELECT CAST(identifier AS VARCHAR) AS with_cast, identifier::VARCHAR AS with_colons
+FROM documents
 ```
 
-Both forms work. `TRY_CAST` returns null instead of erroring on a value that
+Both forms work. Give each its own alias when one projection uses both: they
+produce the same expression name, and a projection refuses two columns with
+one name. `TRY_CAST` returns null instead of erroring on a value that
 will not convert, which is the one to use over a column you do not control.
 
 ## Precedence {#precedence}