Feat/cs/perf++

[ReagentX]

• Memory layout:
  • Type table Vec<Vec<Type>> → Vec<TypeEntry>
  • Archived::Object.data Vec<Vec<OutputData>> → ObjectData
  • The common single-type / single-value case is stored inline with no Vec allocation
  • Type now derives Copy
• Lazy property groups: Property::Group wraps a PropertyGroup that resolves items on demand (yielded by value) instead of materializing a Vec<Property> per group.
• Decode refactor: new Group enum (Empty/One/Many) threads the inline single-value path through read_types; split into read_value / read_embedded; each Type is fetched once and passed by value (no repeated type-table re-indexing).
• Iterative parsing: read_signed_int / read_unsigned_int reference-tag skipping is now a loop instead of recursion.
• Allocation tuning: table capacity is reserved after header validation (not in new) and right-sized to measured density, so malformed/oversized buffers no longer pre-allocate.
• Behavior change: object references that don't resolve during iteration now surface as Property::Primitive rather than being silently dropped (reachable only on malformed streams).