feat(cast): bring remaining --json outputs into JsonEnvelope

[mablr]

Description

Towards OSS-239 (almost there after wallet follow-up)

Move print_scalar, print_list, print_tokens, and print_json_object from local helpers in args.rs into foundry_cli::json so every cmd module can import them directly instead of inlining the if/else pattern.

Replace all remaining inline if shell::is_json() { sh_println!(...) } patterns across cmd modules:

• estimate, find_block, call, mktx → print_scalar
• txpool (all variants), rpc, vaddr/create → print_json_object
• keychain list/inspect/doctor → print_json_object / print_json_success
• erc20 name/symbol/decimals → print_scalar
• erc20 balance/allowance/total_supply → print_json_success (keep format_uint_exp for plain-mode display)
• Block and Tx in args.rs → parse pre-formatted JSON string and wrap
• Selectors in args.rs → new SelectorInfo struct, envelope-wraps array
• AbiEncodeEvent in args.rs → new EncodedEvent{topics,data} struct
• interface → wrap ABI array in envelope on stdout path

Documented explicitly unsupported commands with inline comments: send (N::ReceiptResponse lacks Serialize), logs --subscribe (streaming), wallet (follow-up), upload-signature (external API), four-byte-calldata (interactive).

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes (for commands that already output JSON by default)

[mattsse]

Requesting changes: these paths can fail or emit invalid JSON for valid --json usages.

P1: cast call --json reparses response as JSON, but Cast::call returns raw hex when no output is decoded. Valid calls can therefore error on serde_json::from_str. Please avoid reparsing arbitrary display output; return structured data from Cast::call, or wrap raw hex as a JSON string/envelope in the command layer.

P1: cast block --json and cast tx --json also assume output is a JSON object. --raw or scalar field paths such as block hash / tx from can return scalar strings, which either fail JSON parsing or are not objects. Please only call print_json_object for object output, and use a scalar JSON envelope/string path for field selections.

P2: cast mktx prints the expiration status line to stdout before later JSON/scalar output, which corrupts --json output. Please move this to stderr/warning output, suppress it under shell::is_json(), or include it inside the JSON payload.

Please add regressions for cast call --json with undecoded/raw output, cast block/tx --json scalar field paths, and cast mktx --json --expires-at ... producing a single valid JSON document.

[mablr]

Outscoped cast call as it was overlapping with #14774.

Fixed the rest.

[figtracer]

Three focused JSON-output regressions from the local review pass.

[stevencartavia]

crates/cast/src/cmd/vaddr/create.rs — mined salt is lost on register failure

The non---no-register path now calls register(...).await? before printing the salt/registration_hash/master_id/virtual_addresses block. On master those values were printed first.

Reproduced with no signer (so register errors):

master

STDOUT:
Salt:              0x9bf4…155f
Registration hash: 0x0000…e5fd
Master ID:         0x3a96b610
Virtual addresses:
  tag=0x000000000000  0x3A96B610…0000
STDERR:
Error: cast vaddr create requires a signer (...)

PR

STDOUT:  (only the "Mining…/Found salt in…" lines)
STDERR:
Error: cast vaddr create requires a signer (...)

The mined salt is now lost on any registration failure — the user has to mine again (which can take minutes). Suggest restoring the prior order: compute the payload once, print it, then call register. That also lets you collapse the duplicated JSON/plain-text blocks between the no_register branch and the register branch (both currently emit the same payload; print_json_success and print_json_object are equivalent inside if shell::is_json()).

---

crates/cast/src/cmd/keychain.rs — run_list empty case becomes an error

run_list now routes the empty-keys case through sh_err!, which writes to stderr and prefixes Error:. The same situation in run_show still uses sh_println!, so the two siblings disagree.

Reproduced with TEMPO_HOME pointing at a keys.toml containing keys = []:

master:  EXIT 0  STDOUT: "No keys found in keys.toml."  STDERR: (empty)
PR:      EXIT 0  STDOUT: (empty)                        STDERR: "Error: No keys found in keys.toml."

An empty list is a successful result, not an error. Suggest keeping sh_println! here for parity with run_show (or change both).

---

crates/cast/src/cmd/interface.rs — --json stdout and --json -o file shapes diverge

cast interface --json to stdout now wraps the parsed ABIs in a JsonEnvelope, but cast interface --json -o <file> still writes the raw concatenated json_abi strings to the file. Same data, two shapes depending on whether -o is set.

Reproduced with a single-ABI input:

	stdout (--json)	file (--json -o)
master	[ { ...abi... } ]	[ { ...abi... } ]
PR	{"schema_version":1,"success":true,"data":[[{...}]],…}	[ { ...abi... } ]

If file output is intentionally a raw artifact (not wrapped), please call that out (doc/comment + test); otherwise both destinations should share the envelope shape. Note that for multiple interfaces the file content is also several JSON objects newline-joined, which isn't one valid JSON document.