Module orchestrator 

Backfill orchestration: plan units → gate → run each unit through executor::run_expanded under bounded concurrency → record every unit’s terminal outcome in the durable progress marker.

Reuses expand (so every config gate applies) and the executor (so transforms / quality / contract / masking / DLQ / flush-completing cancel all behave exactly like faucet run). Each unit runs the selected root node with:

• ${backfill.*} tokens substituted in its source + sink configs,
• the ${now.*} clock set to the unit’s window start,
• a namespaced row id (backfill::{unit}) so its state key never touches the forward-sync bookmark,
• delivery forced to at-least-once (pair with write_mode: upsert for idempotent replays).

Structs

BackfillOptions

Inputs for one faucet backfill invocation.

BackfillOutcome

Overall backfill result.

UnitReport

Per-unit report line.

Enums

BackfillRange

The requested replay range.

Functions

run_backfill

Run a backfill. Returns the per-unit outcome table; Err only for planning/gating/config failures (unit failures are reported in the outcome and via a non-Ok summary the caller maps to an exit code).