Stabilize json_feed_collector formatting to unblock CI test (pull_request) job

[Copilot]

The CI / test (pull_request) workflow was failing in ruff format --check . due to collectors/json_feed_collector.py being flagged for reformat. This PR applies a minimal code-only adjustment to make the formatter output stable without changing collector behavior.

• Change made (format-stable expression layout)

  • Refactored the location_text fallback/coercion path in _build_listing from a single long inline expression into a two-step assignment.
  • Preserves existing semantics (location_text still resolves from location_text → location → city → empty string, then coerces to str).

• Why this addresses the CI failure

  • Removes the formatter-sensitive long inline expression that CI identified as needing reformat in this file.

location_text_raw = item.get("location_text") or item.get("location") or item.get("city")
location_text = str(location_text_raw or "")