[Fix] Guard unsafe casts on GetEObject(...) results; fixes #32

[samatstariongroup]

Prerequisites

• I have written a descriptive pull-request title
• I have verified that there are no overlapping pull-requests open
• I have verified that I am following the EcoreNetto code style guidelines
• I have provided test coverage for my change (where applicable)

Description

• Resource.GetEObject(string) now honors its documented "or null if it can't be resolved" contract (returns EObject?) and guards against self-recursion, eliminating the stack overflow.
  • New Resource.GetEObject() resolves and type-checks in one step, throwing a descriptive InvalidOperationException that names the offending fragment (covers both unresolved and wrong-type).
• EClass (eSuperTypes), ETypedElement (eType) and EReference (eOpposite) now use the typed resolver instead of raw casts.
• Adds GuardedGetEObjectTestFixture covering unresolved + incorrect-type at each affected location both at the resolver level and end-to-end via Resource.Load.

[github-actions]

Package	Line Rate	Branch Rate	Complexity	Health
ECoreNetto	85%	77%	407	✔
ECoreNetto.Extensions	99%	93%	101	✔
ECoreNetto.HandleBars	99%	98%	60	✔
ECoreNetto.Reporting	83%	71%	181	✔
ECoreNetto.Tools	94%	87%	59	✔
Summary	89% (2133 / 2407)	81% (486 / 602)	808	✔

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud