Replace JAXB/orchestra-repository with XSLT 2.0 + Saxon-HE

[Copilot]

Eliminates io.fixprotocol.orchestra:repository and all JAXB code from the generator module. XML parsing and tree-walking are replaced by four XSLT 2.0 stylesheets driven by Saxon-HE via javax.xml.transform.TransformerFactory. CLI and Maven plugin interfaces are unchanged.

Core change

OrchestraTransformer — the only new Java class:

// Uses Saxon directly; inner MkDirOutputURIResolver auto-creates dirs for xsl:result-document
TransformerFactory factory = TransformerFactory.newInstance(
    "net.sf.saxon.TransformerFactoryImpl", null);
factory.setAttribute("http://saxon.sf.net/feature/outputURIResolver",
    new MkDirOutputURIResolver());

CodeGeneratorJ and DataDictionaryGenerator become thin adapters that forward to OrchestraTransformer.transform(inputFile, stylesheet, outputDir, params).

Stylesheets (src/main/resources/xslt/)

File	Replaces
common.xsl	Shared keys (fieldById, groupById, …) and type-mapping functions
code-generator-fields.xsl	Field .java generation loop in CodeGeneratorJ
code-generator-messages.xsl	Message / component / group / factory / cracker generation
data-dictionary.xsl	DataDictionaryGenerator tree-walk; emits QuickFIX XML via xsl:result-document

Dependency changes

Removed: io.fixprotocol.orchestra:repository, jakarta.xml.bind-api, jaxb-impl
Added: net.sf.saxon:Saxon-HE:11.6 (compile scope — OutputURIResolver API is used directly)

Test surface

CodeGeneratorUtilTest and DataDictionaryGeneratorTest had methods that instantiated JAXB FieldType / Repository objects directly; those are replaced with equivalent tests against the new API. All other tests (OrchestraGoldenFileTest byte-for-byte golden comparison, CodeGeneratorJSessionExclusionTest, plugin mojos) required no logic changes.

[chrjohn]

@copilot
Please integrate underscore logic from pr 95 file
home/runner/work/quickfixj-orchestra/quickfixj-orchestra/quickfixj-from-fix-orchestra-repository/quickfixj-from-fix-orchestra-generator/src/main/resources/xslt/common.xsl
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