fix: race-safe add_processed_item via atomic upsert (#2626)

[chubes4]

Summary

Fixes #2626. ProcessedItems->add_processed_item() raced between its UPDATE and a bare INSERT, so concurrent Action Scheduler workers processing the same source item collided on the flow_source_item unique key. wpdb->insert() logged a hard Duplicate entry DB error to debug.log on every collision (~2,809 entries/day on the events site, blog 7) even though the code caught the duplicate string and returned true afterward.

The unique key was correctly preventing dupes — the bug was that the bare INSERT logged a hard DB error on every race instead of treating "already processed" as a normal no-op.

Fix

Replaced the UPDATE-then-bare-INSERT pair with a single atomic INSERT ... ON DUPLICATE KEY UPDATE keyed on flow_source_item:

• Fresh item → inserted as processed.
• Existing in-flight claimed row → converted to final processed state (new job_id/processed_timestamp, claim_expires_at cleared) — same end state as the old UPDATE path.
• Concurrent racing worker → clean no-op update, no logged Duplicate entry DB error.

A check-then-insert would not be sufficient (the race is between check and insert); this is a single atomic statement. Dedup behavior is unchanged: exactly one row per (flow_step_id, source_type, item_identifier).

Verification

• php -l clean on the changed file.
• composer lint (phpcs) on the changed file exits 0.
• php tests/processed-item-claims-smoke.php → 21 assertions, 0 failures.
• Validated the exact SQL against real MySQL on a temp table with the production schema:
  • pre-existing claimed row → converted to processed, claim cleared
  • two racing upserts on the same item → exactly one row, no duplicate-key error
  • fresh item → inserted normally
  • total rows = one per unique source item (dedup preserved)

Spans the affected handlers (universal_web_scraper, dice_fm, ticketmaster, vision_flyer) since the fix is in the shared write path.

Fixes #2626

[homeboy-ci]

Homeboy Results — data-machine

Lint

✅ lint — passed

ℹ️ Full options: homeboy docs commands/lint
Deep dive: homeboy lint data-machine --changed-since 6ea31fe

Artifacts and drill-down

• CI results artifact: homeboy-ci-results-data-machine-lint-quality-Linux-node24 contains immediate command JSON for this action invocation.
• Observation artifact: homeboy-observations-data-machine-lint-quality-Linux-node24 contains exported Homeboy run history for deeper queries.
• Drill-down: download the observation artifact, then run homeboy runs import <dir>, homeboy runs list, and homeboy runs findings <run-id>.
• Artifacts are attached to the workflow run: https://github.com/Extra-Chill/data-machine/actions/runs/27551393404

Test

✅ test — passed

ℹ️ No impacted tests found for --changed-since 6ea31fe
ℹ️ Run full suite if needed: homeboy test data-machine
Deep dive: homeboy test data-machine --changed-since 6ea31fe

Artifacts and drill-down

• CI results artifact: homeboy-ci-results-data-machine-test-quality-Linux-node24 contains immediate command JSON for this action invocation.
• Observation artifact: homeboy-observations-data-machine-test-quality-Linux-node24 contains exported Homeboy run history for deeper queries.
• Drill-down: download the observation artifact, then run homeboy runs import <dir>, homeboy runs list, and homeboy runs findings <run-id>.
• Artifacts are attached to the workflow run: https://github.com/Extra-Chill/data-machine/actions/runs/27551393404

Audit

✅ audit — passed

• audit — 76 finding(s)
• Total: 76 finding(s)

Deep dive: homeboy audit data-machine --changed-since 6ea31fe

Artifacts and drill-down

• CI results artifact: homeboy-ci-results-data-machine-audit-quality-Linux-node24 contains immediate command JSON for this action invocation.
• Observation artifact: homeboy-observations-data-machine-audit-quality-Linux-node24 contains exported Homeboy run history for deeper queries.
• Drill-down: download the observation artifact, then run homeboy runs import <dir>, homeboy runs list, and homeboy runs findings <run-id>.
• Artifacts are attached to the workflow run: https://github.com/Extra-Chill/data-machine/actions/runs/27551393404

Tooling versions

• Homeboy CLI: homeboy 0.229.11+31568619
• Extension: wordpress from https://github.com/Extra-Chill/homeboy-extensions
• Extension revision: 67a50b29
• Action: unknown@unknown