Function should_skip_candidate 

pub async fn should_skip_candidate(
    client: &Client,
    filter: &ScannerFilter,
    partition: u16,
    eid: &str,
) -> bool

Issue #122: per-candidate filter helper shared by all execution-shaped scanners.

Returns true iff the candidate eid on partition should be SKIPPED by the scanner (i.e. the filter rejects it). A no-op filter never rejects — returns false without issuing any HGET.

eid format

Callers pass eid as the full {fp:N}:<uuid> ExecutionId string — identical to what Lua stores as a ZSET member via ZADD ... A.execution_id and what every scanner reads out of per-partition index ZSETs with ZRANGEBYSCORE. The helper formats format!("ff:exec:{}:{}:core", tag, eid) which produces the canonical double-tagged production key shape ff:exec:{fp:N}:{fp:N}:<uuid>:core — the first tag comes from the partition’s routing hash-tag; the second is the tag baked into the ExecutionId string. Matches ff_core::keys::ExecKeyContext::core / ::tags exactly. Do not strip the prefix — doing so would build a single-tagged key that does not exist in production.

Cost

0 HGET if filter.is_noop(); 1 HGET when only namespace is set (on ff:exec:{fp:N}:{fp:N}:<uuid>:core); 1 HGET when only instance_tag is set (on ff:exec:{fp:N}:{fp:N}:<uuid>:tags); 2 HGETs when both are set. Namespace is checked first (cheaper — touches the already-hot core hash) and short-circuits on mismatch.

Failure mode

On HGET failure the helper returns true (skip), conservatively: leaking a cross-tenant candidate due to a transient read error is worse than the scanner temporarily underclaiming — the next cycle picks it back up once the backend recovers.