fix: show tool execution source

[Iams4kura]

What this PR does / why we need it?

Fixes #6647.

Tool execution records currently show and search the selected tool name in the Trigger Source field instead of the agent, knowledge base, or trigger that invoked it.

Summary of your change

• Restore the annotated source_name in tool execution record responses.
• Apply source-name searches to that annotation instead of tool_name.
• Add a regression test that gives the source and tool distinct names and verifies both behaviors.

Regression evidence

• Before: python -m unittest tools.tests.ToolRecordSerializerTestCase.test_get_tool_records_uses_annotated_source_name -v exited 1 with ('Price Lookup', False).

• After: the same command exited 0 with the fix.

Verification

• python -m unittest tools.tests -v
• .venv/bin/ruff check apps/tools/tests.py
• .venv/bin/ruff check --isolated --select E9,F63,F7,F82 apps/tools/serializers/tool.py apps/tools/tests.py
• .venv/bin/ruff format --check apps/tools/tests.py

Scope

• 2 files changed, +53 / -4 lines

Please indicate you've done the following:

• Made sure tests are passing and test coverage is added if needed.
• Made sure commit message follow the rule of Conventional Commits specification.
• Considered the docs impact and opened a new docs issue or PR with docs changes if needed. No documentation change is required for this behavior correction.