docs: make every sidebar label a capitalized noun

Six groups were verbs -- Manage, Ingest, Train, Operate, Secure, Deploy -- and
now name the thing rather than the action. Four more were sentence case.

The page labels that were verb phrases follow: Add Computed Column becomes
Computed Columns, Refresh Column becomes Column Refresh, Configuring Storage
becomes Configuration, and Explain becomes Query Plans, which is also more
accurate now that the page covers analyze as well.

SQL statement pages take the keyword -- SELECT, DDL, DML, REFRESH, SHOW, EXPLAIN
-- because a statement name is a noun and lowercase Select and Show read as
instructions. Concept pages there keep noun phrases: Joins, Window Functions,
Subqueries, Operators.

Two duplicate labels are resolved on the way. Reranking sat in Semantic Search
labelled Overview despite being the only page on its subject, and the Enterprise
client page sat in SQL Reference labelled SQL next to the reference Overview; it
is Client Connection now.

Title case leaves prepositions and articles lowercase, so Needle in a Haystack
and Hybrid Search on BEIR are already correct and unchanged.

docs/web/sql/explain.mdx

@@ -1,6 +1,6 @@
 ---
 title: "EXPLAIN"
-sidebarTitle: "Explain"
+sidebarTitle: "EXPLAIN"
 description: "Reading the plan for a statement, and measuring it."
 icon: map
 keywords: ["explain", "explain analyze", "query plan", "describe"]

docs/web/sql/join.mdx

@@ -1,6 +1,6 @@
 ---
 title: "Joins"
-sidebarTitle: "Join"
+sidebarTitle: "Joins"
 description: "Combining rows from more than one table, including across namespaces."
 icon: link
 keywords: ["join", "inner", "left", "outer", "cross", "namespace"]

docs/web/sql/refresh.mdx

@@ -1,6 +1,6 @@
 ---
 title: "REFRESH"
-sidebarTitle: "Refresh"
+sidebarTitle: "REFRESH"
 description: "Filling computed columns and bringing materialized views up to date."
 icon: arrows-rotate
 keywords: ["refresh column", "refresh materialized view", "backfill", "cascade"]

docs/web/sql/select.mdx

@@ -1,6 +1,6 @@
 ---
 title: "SELECT"
-sidebarTitle: "Select"
+sidebarTitle: "SELECT"
 description: "Projection, filtering, ordering, and composing queries out of other queries."
 icon: table-columns
 keywords: ["select", "where", "order by", "limit", "cte", "union", "distinct"]

docs/web/sql/show.mdx

@@ -1,6 +1,6 @@
 ---
 title: "SHOW"
-sidebarTitle: "Show"
+sidebarTitle: "SHOW"
 description: "Listing jobs, functions, materialized views, and the errors a job produced."
 icon: list
 keywords: ["show jobs", "show functions", "show materialized views", "show errors", "show tables"]

docs/web/sql/window.mdx

@@ -1,6 +1,6 @@
 ---
 title: "Window functions"
-sidebarTitle: "Window"
+sidebarTitle: "Window Functions"
 description: "Compute over a set of rows related to the current one, without collapsing them."
 icon: chart-simple
 keywords: ["window", "over", "partition by", "row_number", "rank", "lag", "lead"]