docs: add choose-your-module onboarding guide (#651)

* docs: add choose-your-module onboarding guide

* fix(docs): correct export code examples against actual API signatures

- export_to_rdf() returns a string; use export() for file output
- format="json-ld" is invalid; correct value is "jsonld"
- ParquetExporter/LPGExporter/ArangoAQLExporter take file_path as a
  required positional arg, not output= / output_dir= kwargs
- ArangoAQLExporter().export(graph) was missing file_path entirely,
  which would raise TypeError at runtime
- Remove misleading 'with provenance embedded' comment (no such param)

---------

Co-authored-by: KaifAhmad1 <kaifahmad087@gmail.com>

docs/modules.md

@@ -8,6 +8,10 @@ icon: "puzzle-piece"
   Looking for a quick reference? Jump to the [Module Index](#module-index) at the bottom.
 </Info>
 
+<Tip>
+  Not sure which module to use? The [Choose the Right Module](choose-your-module) guide maps 35+ developer goals to modules with code examples — start there if you're orienting for the first time.
+</Tip>
+
 Semantica is organized into **27 modules** across six logical layers. Each module is independently importable: you never pay for what you don't use.
 
 ## Architecture Overview