Use a specific `Literal` to decide how to apply `wrap_kvs` trans functions.

[thorwhalen]

Proposal: Use FirstArgIsMapping(Literal)

A Literal class to mark a function as being one where the first argument is
a mapping (store). This is intended to be used in wrappers such as wrap_kvs
to indicate when the first argument of a transformer function trans like
key_of_id, preset, etc. is the store itself, therefore should be applied as
trans(store, ...) instead of trans(...).

┆Issue is synchronized with this Asana task by Unito

[thorwhalen]

Triage (2026-07): priority: high, Wave 1 — this is the fix vehicle for #9 and #18.

Good news, found during the audit: class FirstArgIsMapping(LiteralVal) already exists at trans.py:2113 but is unused (tagged # TODO: Use this for it's intent!). The design decision to make here is to adopt the explicit opt-in marker (obj_of_data=FirstArgIsMapping(lambda self, data: ...)) and retire the name-based heuristic (self_names / _has_unbound_self, trans.py:419/:424) that misfires on functions whose first param happens to be named self/store/mapping (see #9).

It's a breaking change — pair with a deprecation path + the dependents test-gate. Mechanics: misc/docs/dol_architecture_map.md §5.4.

[thorwhalen]

Implemented in #72. FirstArgIsMapping(LiteralVal) — previously dead code (# TODO: Use this for it's intent!) — is now consumed via a single resolver _resolve_self_convention at all four call sites (_wrap_outcoming, _wrap_ingoing, postget, preset) and exported from dol:

from dol import wrap_kvs, FirstArgIsMapping
wrap_kvs(store, obj_of_data=FirstArgIsMapping(lambda self, data: ...))  # forces (self, data)

It forces the (self, data) convention regardless of parameter names/arity, and is paired with the arity fix for #9. Verified working in every transform slot (key/value, in/out, postget, preset). Closes on merge of #72.