refactor: extract QdrantOps shared helper

[bug-ops]

Summary

• Add QdrantOps helper in zeph-memory consolidating common Qdrant operations (ensure_collection, upsert, search, delete, scroll)
• Refactor 4 stores (QdrantStore, CodeStore, QdrantSkillMatcher, McpToolRegistry) to delegate low-level Qdrant calls via QdrantOps
• Net reduction: ~180 lines of duplicated boilerplate removed
• 5 new unit tests for QdrantOps

Closes #298

[codecov-commenter]

Codecov Report

❌ Patch coverage is 27.23404% with 171 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
crates/zeph-memory/src/qdrant_ops.rs	40.76%	77 Missing ⚠️
crates/zeph-index/src/store.rs	5.55%	34 Missing ⚠️
crates/zeph-memory/src/qdrant.rs	5.71%	33 Missing ⚠️
crates/zeph-skills/src/qdrant_matcher.rs	11.76%	15 Missing ⚠️
crates/zeph-mcp/src/registry.rs	29.41%	12 Missing ⚠️

❌ Your patch status has failed because the patch coverage (27.23%) is below the target coverage (60.00%). You can increase the patch coverage or adjust the target coverage.

@@            Coverage Diff             @@
##             main     #304      +/-   ##
==========================================
+ Coverage   80.01%   80.29%   +0.27%     
==========================================
  Files          98       99       +1     
  Lines       23926    23900      -26     
==========================================
+ Hits        19145    19191      +46     
+ Misses       4781     4709      -72     

Files with missing lines	Coverage Δ
crates/zeph-mcp/src/registry.rs	75.06% <29.41%> (+8.18%)	⬆️
crates/zeph-skills/src/qdrant_matcher.rs	51.02% <11.76%> (+9.83%)	⬆️
crates/zeph-memory/src/qdrant.rs	34.86% <5.71%> (+2.10%)	⬆️
crates/zeph-index/src/store.rs	44.80% <5.55%> (+4.22%)	⬆️
crates/zeph-memory/src/qdrant_ops.rs	40.76% <40.76%> (ø)

... and 1 file with indirect coverage changes

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