[BGM-PR-14] Oracle Polling Scheduler and Resume Tailing

[slin1237]

Parent: #1214

Track: Oracle
Suggested milestone group: Slice C

Goal

Finish the Phase 1 Oracle execution path using polling only.

Acceptance Criteria

• Oracle claim scheduling uses polling with the configured background_poll_interval.
• Oracle live stream resume tails by polling for new persisted chunk rows while the response remains non-terminal.
• Oracle sweeper and retry behavior match the shared semantics.
• Integration tests cover live polling tail and claim behavior on a real Oracle instance.

Dependencies

• [BGM-PR-06] Scheduler Core and Sweeper Interfaces #1220
• [BGM-PR-09] Stream Persistence and Resume Read Path #1223
• [BGM-PR-13] Oracle Repository Transitions #1227

Out of Scope

• AQ notifications.