Decompose Embeddings Task in Backlog

[julwrites]

This PR addresses the process of taking the #1 Ranked Backlog item (Gap 12.1.1: Embeddings) and properly scoping it out. Since the task CRITICAL-004 requires architectural additions across new managers, commands, UI views, and testing suites—spanning more than 3 files—it was broken down into 3 smaller, sequential sub-tasks:

1. Gap 12.1.1a: Core Logic for embeddings_manager.lua.
2. Gap 12.1.1b: UI/Commands integration.
3. Gap 12.1.1c: Testing suite coverage.

The unranked gaps and ranked backlog lists in BACKLOG.md were appropriately updated and renumbered while preserving their highest priority status.

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PR created automatically by Jules for task 10240964668877803146 started by @julwrites

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