Dead code: `JobRegistry::bump_event_seq` is never called

[nficano]

Category: bug Severity: minor
Location: crates/arcp-runtime/src/runtime/job.rs:194-203
Spec: n/a

What

bump_event_seq (a #[must_use] public method that increments a job's last_event_seq) has no callers anywhere in the workspace — the writer uses record_event_seq instead. It is dead surface that implies a per-job sequence-bumping path that does not exist, and risks future callers mixing two inconsistent sequence-tracking mechanisms.

Evidence

grep -rn bump_event_seq crates/*/src returns only the definition at job.rs:198. The writer path uses record_event_seq (server.rs:359).

Proposed fix

Remove bump_event_seq, or document/test it as the canonical per-job increment and route the writer through it. Don't leave two seq-tracking entry points.

Acceptance criteria

• No unused public seq-mutation method remains, or it is wired and tested as the single source of truth.