fix: #3621936 Fix agent process crash from a bad bundle-filter scalar value

Summary

A scalar string from the LLM (e.g. {"value":"tags"}) instead of a keyed map overrides a bundle (content type/vocabulary) filter's array-typed default. Views' Bundle filter plugin does not validate this before save(): Bundle::calculateDependencies() calls array_keys($this->value), which throws a \TypeError - not an \Exception - when $this->value is a string, crashing the whole PHP process rather than just the one tool call.

Changes

• src/Plugin/AiFunctionCall/UpdateViewHandlerOptions.php: wraps the handler save (setHandler()/mergeDefaults()/save()) in try/catch (\Throwable $e), deliberately wider than \Exception since the real failure is a \TypeError. Returns a normal, readable tool result on failure instead of letting the error propagate.
• config/install/ai_agents.ai_agent.views_agent.yml: documents the correct keyed-map shape for bundle/type filters (plugin_id "bundle"), with an explicit warning against both the bare-string and plain-list mistakes.
• tests/src/Kernel/Plugin/AiFunctionCall/UpdateViewHandlerOptionsTest.php: added testScalarValueForBundleFilterDoesNotCrash().
• tests/src/Kernel/Integration/ConfigureBundleFilterTest.php (new): added testScalarValueIsRejected(), reproducing the same mistake through the real create-handler-then-update-it tool chain and confirming the rejected value was never saved.

Test plan

• Both new regression tests confirmed failing before the fix (uncaught \TypeError) and passing after.
• Full suite passes on this branch in isolation: 11/11 tests, 97 assertions, across both test files, no failures.
• phpcs --standard=Drupal,DrupalPractice and phpstan analyse (module config, level 1) clean on all changed PHP files.

Closes #3621936

AI-Generated: Yes (Used Claude Code to identify the bug while testing the shipped Views Agent against a live LLM, trace the root cause to Drupal core's Bundle filter plugin, implement the fix, and write both regression tests.)