fix: assorted robustness and clarity fixes

[csviri]

Three unrelated small items found while auditing.

ManagedInformerEventSource.get could throw instead of falling back to the
informer cache. It compared a temporary-cache hit against
manager().lastSyncResourceVersion(namespace) without guarding either
failure mode:

• lastSyncResourceVersion is null until an informer has completed its
  initial list, and compareResourceVersions dereferences it, so this
  threw a NullPointerException.
• InformerManager.lastSyncResourceVersion does getSource(ns) .orElseThrow(), which throws NoSuchElementException for a namespace
  that is no longer watched after a dynamic namespace change - a window
  that only closes on the next re-list, when checkGhostResources prunes
  the entry.

TemporaryResourceCache.putResource already guards the null case; the
comparison is now extracted into a helper that guards both and falls back
to the informer cache, which is the safe answer in either case.

ExpectationResult.name() threw a bare NullPointerException when no
expectation was registered, which is a normal result state produced by
ExpectationManager.checkExpectation. It now throws
IllegalStateException pointing at isExpectationPresent(), and says so
in the javadoc.

ResourceOperations cleanups: drops the options parameter of
desiredForJsonPatch, which was never read at any of its six call sites,
and rewrites the comment on create - it claimed the operation "check if
the resource already exists", which it does not; the actual reason
filtering is safe is that the API server rejects a duplicate create.

Part of #3517

[Copilot]

Pull request overview

This PR delivers a small set of robustness and clarity improvements across the operator framework core, primarily addressing edge cases in informer cache reads, improving error reporting for missing expectations, and simplifying internal patch helper APIs.

Changes:

• Prevent ManagedInformerEventSource.get from throwing when last-sync resource versions are unavailable or namespaces are no longer watched, preferring the informer cache in those cases.
• Improve ExpectationResult.name() behavior and documentation by throwing a descriptive IllegalStateException when no expectation is present.
• Clean up ResourceOperations by removing an unused internal parameter and correcting/improving create-event-filtering comments.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/expectation/ExpectationResult.java	Adds a guard + clearer exception and Javadoc for name() when no expectation is registered.
operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/ManagedInformerEventSource.java	Extracts resource-version comparison into a helper and adds guards to fall back to informer cache in problematic cases.
operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/reconciler/ResourceOperations.java	Removes an unused internal parameter from JSON patch desired-state creation and clarifies create filtering comments.