AlgoScan

Crate:
- arc89: validate metadata size at the decode() boundary (reject > MAX_METADATA_SIZE);
  normalize the short-metadata identifier bit in compute_hash/set_hash so the
  hash always reflects the body size per ARC-89; expand the method-constant set
  to the full registry interface.
- asa: NftMint::fractional now validates decimals in 1..=19 (returns
  InvalidFractionalDecimals) — fixes the 10u64.pow overflow and the decimals=0
  inconsistency with is_fractional_nft.
- url: encapsulate Cid (private fields + v0/v1 constructors + accessors) so an
  invalid CIDv0 codec state is unrepresentable; return UnsupportedCid (not
  MalformedCid) for unsupported v1 multicodecs.
- royalty: clamp royalty_basis to MAX_BASIS_POINTS (10000) in royalty_for to
  prevent u128->u64 truncation; add the constant.
- arc69: require `standard` on the wire (drop the serde default) so a note that
  omits it is rejected by from_note.
- indexer: give Arc74Client a 30s default request timeout (+ with_timeout).

Docs:
- ADR: sync the D2 feature example with the shipped manifest (only `fetch`);
  add a language to the D3 fenced block (markdownlint MD040); fix the
  self-contradicting "Status is Proposed" line under an accepted ADR.

examples/nft/mint_arc19: use Cid::v1 for the encapsulated constructor.

The examples/nft/* programs require `["nft", "algod"]`; with `nft` off by
default, the default clippy/check/test runs skipped them. Add `--features
nft` to the steps that compile examples:

- Makefile: `clippy` and `test` targets (so `make ci` builds and lints them).
- CI (general.yml): `cargo-check`, `cargo-clippy`, `cargo-test` jobs.

`nft` is additive (default-off), so enabling it on the --all-targets /
--examples steps is strictly more coverage and cannot mask a default-build
breakage. The wasm-check job stays default.

Organize every example under examples/<category>/ — client, contract,
app, asset, transaction, account, logic_sig, wallet, nft — with explicit
[[example]] path entries. The example `name` is unchanged, so
`cargo run --example <name>` keeps working.

Move the NFT examples out of algonaut_nft/examples and into examples/nft,
and rewrite them against a live algod instead of mocking: real
suggested_params, submit, and real asset ids returned from the network
(no DemoParams stub, no hardcoded AssetId). Gated on
required-features = ["nft", "algod"]:
- nft_mint_arc3   — pure NFT, ARC-3 off-chain metadata
- nft_mint_arc19  — mutable NFT; mint then UpdateAsset the reserve
- nft_mint_arc69  — on-chain metadata in the acfg note
- nft_soulbound   — full ARC-71 issue/hold/revoke across issuer + funded holder
- nft_arc89_box   — mint for a real id, build the ARC-89 box offline