feat: extract DailyMemoryStorage interface with pluggable storage filter

[chubes4]

Summary

One filter to swap the entire daily memory storage backend:

add_filter( 'datamachine_daily_memory_storage', function ( $default, $user_id, $agent_id ) {
    return new MyWordPressDailyMemory( $user_id, $agent_id );
}, 10, 3 );

Supersedes #1050 (closed) which used 5 per-operation filters — that was a code smell pointing at missing abstraction.

What changed

1. New DailyMemoryStorage interface (inc/Core/FilesRepository/DailyMemoryStorage.php)

   • Contract: read, write, append, delete, list_all, search
   • Same signatures the existing DailyMemory class already has

2. DailyMemory implements DailyMemoryStorage

   • Zero behavior change — just adds implements DailyMemoryStorage to the class declaration

3. DailyMemoryAbilities resolves storage via filter

   • New private resolveStorage($user_id, $agent_id) method
   • Fires datamachine_daily_memory_storage filter with the default DailyMemory instance
   • All 5 ability methods use the resolved storage instead of hardcoding new DailyMemory()
   • Safety fallback: if filter returns non-DailyMemoryStorage, falls back to default

4. Removed datamachine_daily_memory_archived action from DailyMemoryTask

   • Duplicative — the pre_archive filter handles write override, the storage interface handles read-back
   • Added cross-reference to datamachine_daily_memory_storage in the pre_archive docblock

How Intelligence uses this

Intelligence hooks one filter and returns its own DailyMemoryStorage implementation that stores/reads daily memory as WordPress pages. One hook, total replacement. Data Machine doesn't know or care what's behind the interface.

add_filter( 'datamachine_daily_memory_storage', function ( $default, $user_id, $agent_id ) {
    $agent = get_agent( $agent_id );
    if ( $agent && ! empty( $agent['agent_config']['intelligence_kit'] ) ) {
        return new Intelligence_WordPress_Daily_Memory( $user_id, $agent_id );
    }
    return $default; // Non-Intelligence agents keep flat files.
}, 10, 3 );

Files

File	Change
inc/Core/FilesRepository/DailyMemoryStorage.php	New — interface with 6 methods
inc/Core/FilesRepository/DailyMemory.php	Add implements DailyMemoryStorage
inc/Abilities/DailyMemoryAbilities.php	resolveStorage() + filter, all methods use it
inc/Engine/AI/System/Tasks/DailyMemoryTask.php	Remove datamachine_daily_memory_archived action