[tisonkun]

Summary

• Simplify the current estimated_size implementations while keeping all 17 public documentation comments implementation-neutral.
• Include size_of::<P>() for TupleSketch and the shared union/intersection state so potentially large inline policy payloads are represented. Built-in zero-sized policies are unchanged.
• Keep CpcWrapper without estimated_size: it contains only fixed-size cardinality metadata and owns no variable-sized storage.
• Unify all 11 internal helper comments as Returns an estimate of memory usage in bytes.
• Convert size assertions to literal snapshot values rather than deriving expectations from formulas. Retain non-circular behavioral comparisons for buffer reuse, shallow generic values, and policy-size coverage.
• Describe the result in the changelog as implementation-dependent rather than a stable accounting contract.

Implementation notes

The inline audit found no configuration-scaled inline buffers in the covered types. Substantial variable-sized state is owned by Vec or Box<[T]>. Custom Tuple policies can have large inline payloads and are now included through size_of::<P>(); generic values' recursively owned allocations remain a separate design topic in #193.

No KLL/REQ methods are added. Public method documentation remains a single sentence that does not prescribe heap, inline layout, capacity, or generic traversal rules.

Validation

• cargo x check
• cargo x test
• cargo x lint