[brenzi-agent]

Every name can be registered only by someone who accepts the terms its name policy keeps: the community terms for a community name, the general terms for any other (simplex-network/ens-contracts#40, #42, #45, and the terms links of simplex-network/ens-contracts#47). A lookup answers an available name as plain available, so a client cannot show the buyer which terms registering it means accepting.

This PR adds those terms to name lookups, behind a new SMP version.

The first commits only change the type, for review before the rest. The name policy keeps two links, each to one file at one commit on git.simplex.chat, with the file's sha256 in the link: the general terms, and the community terms of community names, which include the relevant general ones. A buyer accepts the link's keccak256. NRAvailable gains nameTerms :: Maybe NameTerms, holding either:

• NTGeneral with the general terms (JSON tag general);
• NTCommunity with a community name's community terms (JSON tag community).

Either one carries a TermsDoc:

• termsLink, the link the name policy keeps;
• termsZstd, the linked file in one zstd frame, when it fits the answer.

A client hashes the link to accept the terms, and shows the frame's text after checking its sha256 against the link. A router that sends another link or file only makes that check or the acceptance fail: the name policy compares the accepted hash with the current one. The frame is base64url in JSON, as other bytes are. On the SMP wire it will travel outside the JSON, so it costs no base64: about 15.8 KB fits, and the 39 KB PRIVACY.md compresses to 12.4 KB at zstd 19. nameTerms is absent only from a router before v24, as expires is from one before v22. The three tests that build an NRAvailable set it to Nothing.

Still to come, after the type is agreed:

• the SMP version bump that gates the field;
• RNAME carrying the frame as bytes after the JSON, and the router attaching the frame by what fits the block, directly and through a proxy;
• the resolver reading communityNames and the applicable link (generalTermsLink or communityTermsLink) from the name policy, fetching the file at the link's commit and checking its sha256;
• the spec and the tests.

/Names resolver tests/
/RSLV functional API tests/