docs(changesets): fix the pending release notes

[Imod7]

Description

Fixes the prose in three of the seven changesets parked for the 0.22.0 wave, and records the
convention that would have caught the main omission. No code. Nothing is promoted to
.changeset/, so this publishes nothing.

Changes

pending-changesets/host-ring-vrf-sign.md: declares ringVrfSign as a required member of
the exported AccountsProvider. Wording and wrapping copied from accounts-sign-vrf.md,
which documents the same kind of break for signVrf.

pending-changesets/host-chain-discovery.md: the explicit getChainAPI(env) form is
unchanged only on legacy hosts. On a discovery-capable host it throws
EnvironmentMismatchError when the host's asset hub genesis matches a different bundled
environment, and GenesisMismatchError when it matches none and the bundled asset hub
descriptor disagrees. Both surface at the call, not at the first storage read.

pending-changesets/truapi-09-ring-vrf-keys.md: findRingVrfKeyHandle is exported from
@parity/product-sdk-host, not from @parity/product-sdk-signer, which re-exports the
ring-VRF types only. Also why the inline comparison is a trap: the helper matches the
junction path in order and compares chain and collection ids case-insensitively, so a
shortcut checking only chainId can pick a key registered for a different ring on the same
chain.

pending-changesets/README.md: new Declare required-member additions subsection, so the
next author states the break instead of rediscovering the need for it. Quotes the pattern
inline rather than pointing at accounts-sign-vrf.md, which is deleted once the wave is
consumed.

Why these changes

Four members became required on AccountsProvider since host 0.15.1: listRingVrfKeys,
registerRingVrfKey, ringVrfSign and signVrf. Three were documented, ringVrfSign was
not. Implementations and hand-rolled test doubles break at compile time even though no
caller changes, so the break is invisible to anyone reading only call sites.

The chain-discovery changeset said calls passing an environment keep the previous behaviour
on legacy hosts, which is true, and said nothing about discovery-capable hosts, where an
unchanged call site can now fail earlier and with a different error type.

[github-actions]

📦 Bundle size impact

Comparing 2026-08-19T09:22:13.671Z → 2026-08-19T09:21:21.543Z

No size changes detected. 🟢