fix(storage): recover edge vector indices from a single vector source - #4959

Summary

Edge vector index recovery had the same structural problem that #4953 fixed for vertex vector indices: the vector for each edge lived in a per-index side table that was only as complete as the snapshot's usearch export, and every replay and rebuild step trusted that table and the tag's own ids. This PR ports the single-map design to edges.

Edge types never change, so the label-ordering class of bugs from the vertex fix has no edge analogue. Three problems remain and are addressed here:

1. Silent embedding loss. The snapshot writes the edge section first, resolving each tag's floats from the live index, and exports the usearch contents later. A vector removed in a transaction that later aborted is present in the edge section but absent from the side table. RecoverIndex then fell back to AddEdgeToIndex, which asked the index being built for the vector, got an empty vector, and UpdateVectorIndex treated that as an abort. The edge ended up tagged as a member with no usearch entry and no floats anywhere, with nothing logged.
2. Dangling id after drop. UpdateOnIndexDrop only visited edges present in the dropped index's side table. A tagged edge missing from it kept the dropped id. Every later read of the property went through IndexedPropertyDecoder, asked a nonexistent index, and threw. If a second index on the same property was recovered afterwards, AddEdgeToIndex read the dropped id first and threw during recovery, aborting every restart.
3. Rebuild order. The edge-type+property and global edge property rebuilds ran before the edge vector rebuild, so they indexed the plain-list form of a property that the vector rebuild then converted to a tag.

Changes

• vector_edge_index.hpp/.cpp: VectorEdgeIndexRecoveryInfo holds only the spec. VectorEdgeIndexRecovery::EdgeVectors is one PropertyId -> (Gid -> vector) map. RecoverIndex is replaced by RecoverAllVectorEdgeIndices, a single pass that sets up every index, reads each edge's vector once (from the map for tags, from the store for lists), decides membership from the edge type and the surviving specs, and rewrites the tag only when the stored ids differ. UpdateOnSetEdgeProperty captures the tag's vector when a spec covers the property, erases the entry for any other value, and demotes a tag on an uncovered property to a plain list. UpdateOnIndexDrop walks all edges to demote tags only when the last spec on a property goes.
• snapshot.cpp: LoadPartialEdges captures each tag's vector before InitProperties discards it, merging into the shared map once per batch under a mutex. The vector section of the snapshot only fills gaps with try_emplace. All loaders from v22 onward pass the sink through LightEdgeLoader::RecoverEdges.
• wal.cpp: the edge SET_PROPERTY hook runs before the property store consumes the value, while the decoded WAL value still carries the floats. Label-style incremental bookkeeping is gone.
• durability.cpp: the edge vector rebuild moves ahead of the edge-type+property and global edge property rebuilds.
• metadata.hpp: adds edge_vectors to the recovered indices metadata.

On-disk formats and runtime paths are unchanged.

Tests

Unit (tests/unit/vector_edge_index.cpp):

• RecoverAllVectorEdgeIndicesFromEdgeVectors: every edge stored as a bare tag with vectors only in the map, which is what the edge section provides when the index section lacks the gid. On master this state indexed nothing.
• DropThenRecreateOnSamePropertyRecoversFromEdgeVectors: tagged edges, drop the only index, create a new one on the same property. On master the drop left the tag pointing at the dropped index and the new index's rebuild threw.
• RecoverAllVectorEdgeIndicesResolvesEachEdgeState: plain list with a stale map entry, tag matching no spec, tag matching one of two specs, tag with no vector.
• UpdateOnSetEdgeProperty* and UpdateOnIndexDrop*: capture, erase, orphan demotion, last-spec demotion with the null path, surviving-spec preservation.
• The three existing populate tests are ported to the new entry point.

E2E (tests/e2e/durability/durability_with_vector_edge_index.py): a parametrized replay test with nine scenarios covering edge-before-index, repeated updates, drop, drop-then-recreate, two indexes on one property, and snapshot-then-WAL variants. These guard the new capture and map paths through real files. The two crash and loss scenarios above are only reachable through a snapshot-time race and are reproduced at unit level.

Not built or run locally. CI will verify.