refactor: extract QdrantOps shared helper

[bug-ops]

Context

Four crates duplicate Qdrant boilerplate (~200 lines total): client construction, ensure_collection, upsert_points, search_points with cosine similarity.

Crate	Store struct	Collection
zeph-memory	QdrantStore	zeph_conversations
zeph-index	CodeStore	zeph_code_chunks
zeph-skills	QdrantSkillMatcher	zeph_skills
zeph-mcp	McpToolRegistry	zeph_mcp_tools

Proposed change

Extract QdrantOps helper into zeph-memory (which already exports ensure_qdrant_collection):

pub struct QdrantOps {
    client: Qdrant,
    collection: String,
}

impl QdrantOps {
    pub fn new(url: &str, collection: &str) -> Result<Self, Box<QdrantError>>;
    pub async fn ensure_collection(&self, vector_size: u64) -> Result<()>;
    pub async fn upsert(&self, points: Vec<PointStruct>) -> Result<()>;
    pub async fn search(&self, vector: Vec<f32>, filter: Option<Filter>, limit: u64) -> Result<Vec<ScoredPoint>>;
    pub async fn delete_by_filter(&self, filter: Filter) -> Result<()>;
    pub fn client(&self) -> &Qdrant;
}

Each domain store keeps its logic but delegates low-level Qdrant calls.

Affected crates

zeph-memory (new module), zeph-index, zeph-skills, zeph-mcp

Complexity

Medium

References

.local/plan/architecture-audit.md — Phase 2, item 2.1