Include source line numbers in query result locations

[AshwaniKharwar]

Summary

Add source line numbers to query-result locations so AI agents and developers can open the relevant code directly, reducing exploratory reads and token usage.

Proposed behavior

• Preserve each node's parsed source line in flow/query steps.
• Render known locations as path/to/file.py:line in the Markdown result table.
• Keep the current file-only output when line metadata is unavailable.

Acceptance criteria

• Query/flow result steps include the parsed line number when available.
• Markdown output appends the line number only for known values.
• Existing consumers retain their current fields and behavior.
• Tests cover known and unknown source-location cases.