somnia v0.5.2

Completes the P1 roadmap tier. Every change is API-additive (new builders,
methods, a defaulted trait method, and new SurrealQL impls), so this stays a
patch release; the only behavioral shift is that collection fields now emit a
more precise array<…> type in generated DDL.

Added (0.5.2)

• Recursive graph paths — the Path node gained recurse_all() (@.{..}),
  recurse_up_to(n) (@.{..n}), recurse_range(min, max) (@.{min..max}), and
  recurse_exact(n) (@.{n}), rendering SurrealDB's recursive traversal syntax
  (relative @.{…} or, with from_record, record-anchored). Validated against a
  live in-memory engine.
• DEFINE INDEX — a runtime DefineIndex builder (plain, composite,
  unique(), search(analyzer), hnsw/mtree vector, comment,
  concurrently, overwrite, and DefineIndex::remove) plus a repeatable derive
  attribute #[index(name = "…", fields = "a, b", unique)]. Derived indexes flow
  into the new SurrealSchema::define_indexes() and are emitted by up() after
  the field definitions. A live test confirms a UNIQUE index rejects duplicates.
• Richer field types — the derive maps Rust types via real recursive
  syn::Type analysis instead of substring matching: typed arrays
  (Vec<T>/VecDeque/HashSet/slices → array<…>), arrays of records, nested
  Option, duration, and decimal. Adds SurrealQL literal impls for
  Vec<T> (renders […]) and std::time::Duration (renders e.g. 1s500000000ns).

Changed (0.5.2)

• SurrealSchema gained a defaulted define_indexes() method; existing manual
  implementations are unaffected.
• The derive emits a precise array<…> element type for collection fields
  (previously a bare array). Generated DDL only; no Rust API change.