* docs: improve SHACL validation guide onboarding and workflow guidance
* docs: fix SHACL validation implementation mismatches
* docs: fix stale violation URIs and drop unused imports in SHACL guide
Step 5's illustrative explain_violations() output still referenced the
old cti.example.org/data/... node URIs after Step 4's data_ttl was
rewritten to use example.org/... URIs. Also removes now-unused
export_rdf/tempfile/os imports left over from replacing dynamic RDF
export with inline Turtle strings in five of the code examples.
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Co-authored-by: KaifAhmad1 <kaifahmad087@gmail.com>