[WIP] Add semantic clustering and correction learning for resolution engine

[Copilot]

Thanks for assigning this issue to me. I'm starting to work on it and will keep this PR's description up to date as I form a plan and make progress.

Original prompt

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This section details on the original issue you should resolve

<issue_title>feat(resolution): semantic merchant clustering + correction learning</issue_title>
<issue_description>## Summary
Phase 3 intelligence layer for the resolution engine.

Requirements

• Embed merchant/entity descriptions (via ai-providers or local model)
• Cluster semantically similar transactions (not just text matching)
• Learn from user corrections: when user re-categorizes, update resolution model
• Generate explanation objects: "Classified as Groceries because: similar to previous Trader Joe's transactions, amount range matches, weekly pattern"

Acceptance

• Semantic clustering finds related merchants that text matching misses
• User corrections improve future resolution accuracy
• Explanations are generated for all resolutions</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes feat(resolution): semantic merchant clustering + correction learning #73

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[kayodebristol]

Closing this PR to enforce the 1-PR-per-repo rule. Only one Copilot PR is allowed per repository at a time. The oldest PR (#48) will be kept active.