feat(weave): store call views in CallViewSpec objects

[bcsherma]

Summary

Changes view storage from summary.weave.views blob to a dedicated CallViewSpec object referenced by view_spec_ref. This enables content-addressed deduplication of identical view configurations across calls.

Changes

• Add CallViewSpec builtin object class with typed view item schemas:
  • ContentViewItem: base64-encoded content with mimetype
  • TableRefViewItem: reference to a Table object
  • ObjectRefViewItem: reference to a SavedView or other object
  • ScoreSummaryWidgetItem, ChildPredictionsWidgetItem: widget markers
• Register CallViewSpec in builtin_object_registry
• Add _pending_views field to Call for collecting views during execution
• Update set_call_view to store in _pending_views instead of summary
• Add build_and_save_call_view_spec to create and save CallViewSpec at call_end
• Update weave_client to call build_and_save_call_view_spec and set view_spec_ref
• Update tests to verify new storage format

[bcsherma]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• feat(weave): embed SavedViewDefinition directly in CallViewSpec #6018
• feat(weave): add on_complete callback to Evaluation #6011
• feat(weave): store call views in CallViewSpec objects #6010 👈 (View in Graphite)
• feat(weave): add Widget types and extend set_view for complex items #6009
• feat(weave): add view_spec_ref column to call schema #6008
• master

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[codecov]

Codecov Report

❌ Patch coverage is 77.27273% with 15 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
weave/trace/view_utils.py	60.52%	8 Missing and 7 partials ⚠️

📢 Thoughts on this report? Let us know!

[github-actions]

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[bcsherma]

Consolidated into #6019