🐛 Let the engine quote the Arrow field names it interpolates

`node-batch` named every top-level Arrow field with backticks, so that a
column whose name is a reserved word (`Page.index`, `Document.options`)
survived the DDL Ladybug generates for a staged table. The engine now
quotes those identifiers itself, and it does not collapse a doubled
backtick, so a pre-quoted name reaches the parser as ``index`` and
`createArrowTable` fails outright:

    Parser exception: mismatched input '``' expecting PRIMARY

Name the fields with `column-name`. The `COPY` projection is Cypher
rather than DDL and keeps its own backticks through
`cypher-property-key`, and STRUCT member names keep theirs too: those
come out of `LogicalType::toString()`, which the DDL builder does not
touch, so an unquoted member called `column` still fails to parse.

Measured with `probes/arrow/probe25.clj` against lbug 0.19.1: a plain
top-level reserved word loads and reads back, a pre-quoted one fails to
parse, a plain STRUCT member fails to parse, and a pre-quoted one loads
and reads back.

Also re-dates the engine facts in the `app.graph.arrow` docstring to the
version they were checked against, drops the SIGSEGV note from
`->param-value` now that `Connection.execute` rejects an unwrapped
parameter, and removes two references to the CSV loader.

AI-assisted-by: mixed models

backend/src/app/graph/arrow.clj

@@ -9,11 +9,9 @@
 
   Rows are built as Arrow `VectorSchemaRoot`s in the JVM's off-heap memory,
   handed to Ladybug as a virtual table, and `COPY`d into the real one. No file
-  is written and no text is parsed, which is the whole point: the CSV path had
-  to serialize every value into a literal Ladybug re-parsed, and its inner
-  parser has no escaping at all, so a third of the old loader existed to detect
-  and route around that (`app.graph.bulk`, since deleted). Arrow carries MAP,
-  STRUCT, fixed-size arrays and multi-line strings natively.
+  is written and no value is rendered as text for the engine to re-parse, so
+  nothing in this path needs escaping. Arrow carries MAP, STRUCT, fixed-size
+  arrays and multi-line strings natively.
 
   The type language is Ladybug's, read recursively by `app.graph.schema.values`;
   this namespace adds the matching Arrow `Field` and a writer for each shape.
@@ -21,19 +19,20 @@
   into a packed integer — exactly as it does for the Cypher path, so the two
   writers cannot disagree.
 
-  Engine facts this file depends on, each verified against lbug 0.18.2:
+  Engine facts this file depends on, each verified against lbug 0.19.1:
 
   - An Arrow table is **not** a `COPY` source identifier, but it *is* a
     MATCH-able node label: `COPY T FROM (MATCH (n:stg) RETURN n.a AS a, …)`.
   - A MAP vector's `entries` child struct must be non-nullable, and
     `MapVector/getWriter` silently promotes it to a sparse union — so map
     vectors are built from an explicit `Field` and filled child-first.
-  - Ladybug names a staged struct's fields from the Arrow child names and
-    quotes none of them, so a reserved field name (`column`) must arrive
-    already backticked.
-  - `createArrowRelTable` cannot resolve endpoints against a UUID-keyed node
-    table under any endpoint encoding, so edges are staged as a node table and
-    joined by the `COPY` subquery instead."
+  - Ladybug quotes the column and table names it interpolates into the staged
+    table's DDL, and does not quote a STRUCT member name. So a top-level field
+    arrives plain and a struct member whose name is a reserved word (`column`)
+    arrives backticked.
+  - `createArrowRelTable` resolves a UUID-keyed endpoint only from a
+    `FixedSizeBinary(16)` column carrying the `arrow.uuid` extension, so edges
+    are staged as a node table and joined by the `COPY` subquery instead."
   (:require
    [app.common.json :as json]
    [app.graph.ladybug :as ladybug]
@@ -240,20 +239,19 @@
 (defn- node-batch
   "One `VectorSchemaRoot` holding every projected row of `table`.
 
-  Fields are named with their **backticks** (`cypher-property-key`, not
-  `column-name`): Ladybug derives the staged table's DDL from the Arrow field
-  names and quotes none of them, so a column whose name is a reserved word —
-  `Page.index`, `Document.options` — fails `createArrowTable` outright unless it
-  arrives already quoted. Same rule as for struct field names, and the `COPY`
-  projection below spells them the same way."
+  Fields carry the plain column name. Ladybug quotes every identifier it
+  interpolates into the staged table's DDL, so a name that is a reserved word
+  (`Page.index`, `Document.options`) arrives unquoted and a name arriving
+  pre-quoted comes out doubly backticked and fails to parse. The `COPY`
+  projection below is Cypher, not DDL, so it quotes the same names itself."
   ^VectorSchemaRoot [^BufferAllocator allocator table rows]
   (let [columns (nodes/column-keys table)
-        fields  (mapv (fn [k] (column-field (nodes/cypher-property-key table k)
+        fields  (mapv (fn [k] (column-field (nodes/column-name table k)
                                             (nodes/column-ladybug-type table k)))
                       columns)
         root    (VectorSchemaRoot/create (Schema. ^List fields) allocator)]
     (doseq [k columns]
-      (fill-vector! root (nodes/cypher-property-key table k)
+      (fill-vector! root (nodes/column-name table k)
                     (nodes/column-ladybug-type table k)
                     rows #(get % k) (nodes/column-map-key-fn table k)))
     (.setRowCount root (count rows))

backend/src/app/graph/ladybug.clj

@@ -103,7 +103,7 @@
     :else        (format-string (str v))))
 
 (defn map-type?
-  "Is `ladybug-type` a MAP column? Those cannot be bulk-loaded from CSV."
+  "Is `ladybug-type` a MAP column?"
   [ladybug-type]
   (and (string? ladybug-type)
        (str/starts-with? ladybug-type "MAP(")
@@ -362,11 +362,11 @@
 (defn- ->param-value
   "Clojure scalar → `Value` for prepared-statement binding.
 
-  Every parameter goes through here, unconditionally: an unwrapped value does
-  not raise, it SIGSEGVs the JVM in `lbug_value_clone`. Lists and maps are not
-  supported by the JNI `Value` constructor at all, so `MAP`, `STRUCT` and
-  `T[]` columns stay literal-rendered (`format-typed-value`) — the `:else`
-  raise below means a caller tried to bind one."
+  This is the only `Value` constructor on the write path, so every parameter
+  is wrapped here. Parameters are scalars: the `Value` constructor takes no
+  list or map, so `MAP`, `STRUCT` and `T[]` columns stay literal-rendered
+  (`format-typed-value`) and the `:else` raise below means a caller tried to
+  bind one."
   ^Value [v]
   (cond
     (nil? v)     (Value/createNull)                ; no explicit type needed

backend/src/app/graph/schema/nodes.clj

@@ -9,7 +9,7 @@
 
   Each registry entry declares Penpot Malli sources plus projection
   options (`:drop`, optional `:extra`). Derived artifacts — Ladybug
-  DDL, CSV columns, validation, type dispatch — all flow from that.
+  DDL, Arrow fields, validation, type dispatch — all flow from that.
 
   Column *names* and *types* are not ours to choose: they are the
   contract downstream consumers read, and beadpot owns it. Every
@@ -170,8 +170,8 @@
 (defn column-keys
   "Projected column keys for `table`, in registry order.
 
-  Keys the beadpot contract drops on this table are omitted, so column
-  order, the CSV header and the DDL cannot disagree about what exists."
+  Keys the beadpot contract drops on this table are omitted, so the column
+  order, the Arrow batch and the DDL cannot disagree about what exists."
   [table]
   (into []
         (comp (map first)