[cocolato]

Bounded snapshots currently turn common container subclasses into placeholders that lose their entries and fields. Capture dict/list/tuple/set/frozenset subclasses with builtin-compatible adapters that retain entries, original type names, instance attributes, slots, named fields, and shared references. Python 3.15 frozendict values use portable mapping copies.

Keep item/node selection bounded and avoid application hooks when reading types, entries, and attributes. OrderedDict retains link order for safe keys; custom-key order falls back to insertion order with a visible mapping_order omission. Preserve mutable cycles during pickle/dill state restoration, immutable-key lookup behavior, multiline pretty-printing, and snapshot metadata during recapture. Add targeted regressions and document the captured representation.

Refs #58. Third PR in the series. PRs #59 and #60 are merged, and this PR now targets main; the diff contains the container changes.

Validation:

• CPython 3.13.15 full suite: 151 passed, 2 skipped; coverage 89.64% (85% gate).
• CPython 3.15.0 full suite: 152 passed, including frozendict; the single failure was the existing native PID integration test because macOS denied access to the child process task port. Running that exact test on the unchanged base commit reproduced the same permission error.
• Ruff lint/format checks, git diff --check, and strict Sphinx build passed.
• The three commits together were compared byte-for-byte with all 14 reviewed tracked files; local historical review notes are excluded.

Native PID attachment on this local macOS/Python 3.15 interpreter remains blocked by OS permissions; this does not affect the passing CI matrix below.

CI on the latest head: all 10 checks passed, covering Linux Python 3.11–3.15, Windows/macOS Python 3.14, quality, documentation, and distributions. Workflow run.