fix(plugin-detail): compile the reference rail's parent scope by relationship arity

.changeset/8883-reference-rail-parent-scope-arity.md

@@ -0,0 +1,35 @@
+---
+"@object-ui/plugin-detail": patch
+---
+
+fix(plugin-detail): `record:reference_rail` compiles its parent scope by relationship ARITY, and stops offering a link it cannot express
+
+The rail took an author-supplied `relationshipField` per entry and compiled it
+as bare equality TWICE, in two different grammars: the `$filter` it puts on the
+wire and the `filter[<field>]=<value>` URL its "View All" link points at. When
+the named field is `multiple: true` — `Field.user({ multiple: true })` is the
+platform's own shape — the stored value is an array, `=` asks whether that
+whole array IS one id, and the driver refuses with `400 INVALID_FILTER` while
+prescribing `$contains`. The rail was empty for a perfectly legal authoring
+choice, and for one the platform reaches with no authoring at all: a child
+object's `lookup` field is derived into a rail entry whatever its arity.
+
+The `$filter` half now goes through `composeParentScopeFilter` from
+`@object-ui/core` — the one compiler the related list's rows and its tab badge
+already share — so a multi-value relationship is queried by membership and
+everything else keeps `=` byte for byte. No authoring key was added: the author
+is naming a relationship, and its storage form is the renderer's business. The
+child object's field defs are resolved BEFORE the reads rather than after a
+refusal, because the rail dispatches its queries once per (record + entries)
+and has no second attempt to correct itself with. Resolution is best-effort,
+not a gate: an adapter that cannot serve metadata still reads rows, with the
+equality wire it has always sent.
+
+The link half is the COST. No URL spelling on this surface carries membership —
+the data surface recognises `gte`/`lte`/`gt`/`lt` and drops any other suffix,
+and the route the rail actually links to parses equality only — so a hopeful
+`[contains]` suffix would not narrow the destination at all and "View All"
+would open the entire child table dressed as this parent's related records.
+Rather than ship a rail whose rows and link disagree, the link is suppressed on
+a multi-value relationship and the reason is logged once. Single-value entries
+keep their link with a byte-identical href.