Summary

• Refactors event flyer, vision image, and HTML section selection-time prefilters to use Data Machine core FreshCandidateCollector.
• Removes the old deprecated event import processed-check helper methods instead of leaving compatibility shims.
• Adds coverage showing a processed first HTML section does not stop scanning when a later fresh section exists.

Testing

• php -l on changed PHP files: passed.
• Pure PHP smoke for EventSectionFinder + FreshCandidateCollector: passed.
• git diff --check: passed.
• homeboy test --path /Users/chubes/Developer/data-machine-events@refactor-core-candidate-collector --skip-lint --force-hot -- --filter=EventSectionFinderTest: failed before running tests due a playground/bootstrap database error during Data Machine activation (SQLSTATE[HY000]: General error: 1 no such table: wptests_users).
• homeboy lint --path /Users/chubes/Developer/data-machine-events@refactor-core-candidate-collector --force-hot: failed with 678 pre-existing lint findings in unrelated TS block files.

Closes #229.

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode (openai/gpt-5.5)
• Used for: Refactoring event candidate prefilters onto the Data Machine core fresh-candidate primitive and updating tests. Chris remains responsible for review and merge.