feat: define a materialized view by its query, with Functions in FROM position

A view definition was a structured record under a `kind` tag, one kind
per query shape, and a Function returning `list<struct>` was about to
add a third. That names shapes instead of describing a relation.

A materialized view is now a relation defined by a query, stored as one
canonical SQL string under a format number:

    SELECT columns FROM [ns.]table [, function(args) AS alias | , UNNEST(column) AS alias]
      [WHERE predicate] [LIMIT n]

Any other clause is refused at parse time. Older readers report the view
as unrefreshable, the pre-format layouts still read, and a legacy view is
rewritten on its next refresh that commits, rebuilt only where its raw
text meant something else under lance's parser.

A Function in FROM position yields one row per element it returns, as a
table function does in any dialect. The server stages its list output in
a hidden table and records that binding beside the query, which stays as
the user wrote it; refresh scans the staging and unnests the column, the
same operator as UNNEST over a list column the table already holds. Row
ids repeat per element, so eviction and incremental append are
unchanged. A local database refuses a Function in FROM position, since
it has no executor.

docs/src/js/interfaces/MaterializedViewDefinition.md

@@ -6,64 +6,17 @@
 
 # Interface: MaterializedViewDefinition
 
-The query that defines a materialized view.
+The query that defines a materialized view, as stored:
+`SELECT columns FROM [ns.]table [, function(args) AS alias | , UNNEST(column) AS alias]
+[WHERE predicate] [LIMIT n]`. A Function in `FROM` position yields one row
+per element it returns.
 
 ## Properties
 
-### filter?
+### query
 
 ```ts
-optional filter: string;
+query: string;
 ```
 
-SQL predicate selecting the source rows the view holds.
-
-***
-
-### inputs
-
-```ts
-inputs: string[];
-```
-
-Source columns the projections and filter read.
-
-***
-
-### limit?
-
-```ts
-optional limit: number;
-```
-
-Cap on the number of rows the view holds.
-
-***
-
-### projections
-
-```ts
-projections: [string, string][];
-```
-
-`[output column, SQL expression]` pairs, in view schema order.
-
-***
-
-### sourceNamespace
-
-```ts
-sourceNamespace: string[];
-```
-
-Namespace holding the source table; empty is the root namespace.
-
-***
-
-### sourceTable
-
-```ts
-sourceTable: string;
-```
-
-Name of the source table, in the same database as the view.
+The defining query, in the canonical spelling the server stores.