Gate client-side vocab-doc lookups on ixsl:doc-fetched()

The doc-available()/document(namespace-uri()) branch in ac:property-label
(default.xsl) was unguarded after #298, so on Saxon-JS it fell back to a
synchronous XMLHttpRequest for every property whose namespace wasn't already
in the documentPool. With ?mode= on the source RDF's base URI, document('')
resolved to the page URL and Firefox served the cached HTML representation
to that sync XHR, producing the cascade of "XML Parsing Error: Expected:
</meta>" failures after ldh:set-property-metadata.

ac:property-label is invoked from xsl:sort and can't be made async, so the
fix uses Saxon-JS's own ixsl:doc-fetched() — a synchronous probe of the
internal documentPool (SaxonJS3.rt.js: I.fixed.Ta[$uri]) that triggers no
fetch. Saxon's doc-available() probe is restored with its pre-#298
use-when="...SAXON" guard so server-side behaviour is unchanged.

ac:object-label gets the symmetric addition: the LDH override at
default.xsl:87 had inherited the SPARQL-based $object-metadata branch but
dropped Web-Client's doc-fetch branch entirely, so object URIs whose label
lived in a cached vocab (e.g. skos:Concept, ldh:View) never resolved
client-side. Both processors now have parallel chains: local source RDF →
async-loaded metadata → documentPool/live-fetch → URI heuristics.

rdf.xsl bs2:TypeControl gets the same gating: ac:label(key(..., ...)) stays
unconditional, only the document() source inside key() is wrapped in
if (ixsl:doc-fetched(...)) then ... else () on Saxon-JS to avoid the sync
XHR. xmlns:ixsl declaration added to rdf.xsl since it didn't have one.

Debug xsl:message lines included in all three SaxonJS branches to verify
which lookups take the documentPool path; safe to strip in a follow-up.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: namedgraph

src/main/webapp/static/com/atomgraph/linkeddatahub/xsl/bootstrap/2.3.2/imports/default.xsl

@@ -96,6 +96,13 @@ exclude-result-prefixes="#all"
                 <!-- <xsl:message>ac:object-label(<xsl:value-of select="."/>) $object-metadata: <xsl:value-of select="serialize($object-metadata)"/></xsl:message> -->
                 <xsl:apply-templates select="$object-metadata!key('resources', $this, .)" mode="ac:label"/>
             </xsl:when>
+            <xsl:when test="ixsl:doc-fetched(ac:document-uri(.)) and key('resources', ., document(ac:document-uri(.)))" use-when="system-property('xsl:product-name') eq 'SaxonJS'">
+                <xsl:message select="'ac:object-label doc-fetched HIT: ' || ac:document-uri(.) || ' for ' || ."/>
+                <xsl:apply-templates select="key('resources', ., document(ac:document-uri(.)))" mode="ac:label"/>
+            </xsl:when>
+            <xsl:when test="doc-available(ac:document-uri(.)) and key('resources', ., document(ac:document-uri(.)))" use-when="system-property('xsl:product-name') = 'SAXON'">
+                <xsl:apply-templates select="key('resources', ., document(ac:document-uri(.)))" mode="ac:label"/>
+            </xsl:when>
             <xsl:when test="contains(., '#') and not(ends-with(., '#'))">
                 <xsl:sequence select="substring-after(., '#')"/>
             </xsl:when>
@@ -418,7 +425,11 @@ exclude-result-prefixes="#all"
             <xsl:when test="$property-metadata/key('resources', $this, .)">
                 <xsl:apply-templates select="$property-metadata/key('resources', $this, .)" mode="ac:label"/>
             </xsl:when>
-            <xsl:when test="doc-available(ac:document-uri(namespace-uri())) and key('resources', $this, document(ac:document-uri(namespace-uri())))">
+            <xsl:when test="ixsl:doc-fetched(ac:document-uri(namespace-uri())) and key('resources', $this, document(ac:document-uri(namespace-uri())))" use-when="system-property('xsl:product-name') eq 'SaxonJS'">
+                <xsl:message select="'ac:property-label doc-fetched HIT: ' || ac:document-uri(namespace-uri()) || ' for ' || $this"/>
+                <xsl:apply-templates select="key('resources', $this, document(ac:document-uri(namespace-uri())))" mode="ac:label"/>
+            </xsl:when>
+            <xsl:when test="doc-available(ac:document-uri(namespace-uri())) and key('resources', $this, document(ac:document-uri(namespace-uri())))" use-when="system-property('xsl:product-name') = 'SAXON'">
                 <xsl:apply-templates select="key('resources', $this, document(ac:document-uri(namespace-uri())))" mode="ac:label"/>
             </xsl:when>
             <xsl:otherwise>

src/main/webapp/static/com/atomgraph/linkeddatahub/xsl/bootstrap/2.3.2/imports/rdf.xsl

@@ -22,6 +22,7 @@
 <xsl:stylesheet version="3.0"
 xmlns="http://www.w3.org/1999/xhtml"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+xmlns:ixsl="http://saxonica.com/ns/interactiveXSLT"
 xmlns:xhtml="http://www.w3.org/1999/xhtml"
 xmlns:xs="http://www.w3.org/2001/XMLSchema"
 xmlns:lapp="&lapp;"
@@ -72,7 +73,11 @@ exclude-result-prefixes="#all">
                     </xsl:call-template>
 
                     <label class="control-label" for="{$for}" title="{$this}">
-                        <xsl:value-of select="ac:label(key('resources', $this, document(ac:document-uri(namespace-uri()))))"/>
+                        <xsl:value-of select="ac:label(key('resources', $this, document(ac:document-uri(namespace-uri()))))" use-when="system-property('xsl:product-name') = 'SAXON'"/>
+                        <xsl:if test="ixsl:doc-fetched(ac:document-uri(namespace-uri()))" use-when="system-property('xsl:product-name') eq 'SaxonJS'">
+                            <xsl:message select="'rdf.xsl bs2:TypeControl doc-fetched HIT: ' || ac:document-uri(namespace-uri()) || ' for ' || $this"/>
+                        </xsl:if>
+                        <xsl:value-of select="ac:label(key('resources', $this, if (ixsl:doc-fetched(ac:document-uri(namespace-uri()))) then document(ac:document-uri(namespace-uri())) else ()))" use-when="system-property('xsl:product-name') eq 'SaxonJS'"/>
                     </label>
 
                     <div class="controls">