Avoid duplicating loop-mode queue entries during job retry and stuck recovery

[chubes4]

Problem

Recovering or manually retrying a job that consumed a queued config patch from a queue_mode: loop flow can duplicate the queue entry.

Observed on intelligence-chubes4 Flow 2 (WordPress.com wiki: MGS history queue):

1. Flow 2 fetch step uses config_patch_queue with queue_mode: loop.
2. Job 638 consumed a config patch and became stuck in processing.
3. Running:

   studio wp datamachine jobs recover-stuck --flow=2

   reported Requeued: 1.
4. Flow 2 then had a duplicate performance-mgs config patch.

Root cause

Loop-mode queue consumption already rotates the consumed entry back to the tail:

inc/Abilities/Flow/QueueAbility.php

// Drain or loop: pop the head, optionally rotate.
$entry = array_shift( $queue );

if ( 'loop' === $queue_mode ) {
    $queue[] = $entry;
}

But stuck-job recovery blindly appends the backup again:

inc/Abilities/Job/RecoverStuckJobsAbility.php

$flow_config[ $step_id ][ $slot ][] = $entry;

Manual retry has the same blind append pattern:

inc/Abilities/Job/RetryJobAbility.php

$flow_config[ $step_id ][ $slot ][] = $entry;

For queue_mode: loop, this turns one logical queued patch into two physical entries.

Scope

Fix Data Machine core queue restoration so retry/recovery does not duplicate loop-mode queue entries.

Likely affected files:

• inc/Abilities/Job/RecoverStuckJobsAbility.php
• inc/Abilities/Job/RetryJobAbility.php
• tests covering queued prompt/config patch backup restoration

Desired behavior

• drain mode: restore consumed prompt/config patch on retry/recovery because the item was removed from the queue.
• loop mode: do not append a duplicate because consume already rotated the item back into the queue.
• static mode: no restoration needed; static mode does not mutate queue state.
• Both prompt queues and config patch queues should behave consistently.
• Manual retry and recover-stuck should share the same semantics.

Acceptance criteria

• Tests prove recover-stuck does not duplicate config_patch_queue entries for queue_mode: loop.
• Tests prove manual retry does not duplicate config_patch_queue entries for queue_mode: loop.
• Tests prove drain mode still restores consumed entries.
• If code is duplicated between retry and recovery, extract a small shared helper or otherwise keep the semantics identical.
• No source-specific workaround for Intelligence/MGS/Flow 2.

Runtime evidence

Flow 2 job 638 had a queued_prompt_backup for config_patch_queue and mode: loop. Recovery appended that backup even though the original loop consume had already rotated the entry.

[chubes4]

Fixed by #1811.