feat(near): port NEAR Intents preset (decode + render) and merge converters

[shahan-khatchadourian-anchorage]

Third PR of the NEAR-consolidation stack (stacked on #426). Adds the NEAR Intents preset -- decode + render for the signed-envelope and pre-signature flows -- and merges the crate's two input-format handlers into one.

Stack: A1 (#425) -> A2 (#426) -> A3 (this) -> A4 (signature verification) -> B (identity + wiring) -> C (docs site).

What this PR does

Adds chain_parsers/visualsign-near/src/presets/intents/:

• mod.rs: entry points (try_decode_execute_intents, try_render_single_intent), NearIntentsError, NearTokenRegistry/TokenMeta.
• args.rs: JSON deserialization of execute_intents args.
• tokens.rs: seeded NEP-141 token table + amount formatting.
• render.rs: renders all 11 intent variants (TokenDiff, Transfer, FtWithdraw, NftWithdraw, MtWithdraw, NativeWithdraw, AddPublicKey, RemovePublicKey, SetAuthByPredecessorId, StorageDeposit, AuthCall) plus the signature-status section.
• verify.rs: partial -- only verify_and_extract and the secp256k1 recovery-id guard (render.rs calls these directly to compile). The dedicated signed-vector test module is scoped to A4 (signature verification specifically), since it needs fixture files and dev-dependencies (k256, bs58) not yet added.

near_env_shim.rs does not carry over -- a prior investigation this session found near-sdk 5.27+ (what this workspace resolves) already fixes the native-linking gap that module worked around, so visualsign-near keeps the workspace's unsafe_code = "forbid" outright, no carve-out.

The converter merge (the one non-mechanical step)

tx.rs's NearTransaction becomes an enum:

pub enum NearTransaction {
    OnChain(near_primitives::transaction::Transaction),
    Intent(String), // validated DefusePayload JSON, kept as text
}

from_string tries borsh decode first (via the existing hex/base64 detection); on failure, it validates the input as a DefusePayload JSON envelope. Input that is neither is rejected. This replaces two separate converters -- one per input format, each registered under its own custom chain name -- with a single type discriminating by format, matching the target design (one chain identity, format-discriminated).

convert.rs dispatches on the enum: OnChain renders as before (A2's baseline fields) plus the execute_intents decode branch A2 deliberately omitted, now calling the real preset when the action is a FunctionCall to intents.near/execute_intents; Intent renders via try_render_single_intent, titled "NEAR Intent", with no signature section (nothing is signed yet at that stage).

Security fix folded in

Self-review of this port surfaced a signing-integrity gap: FtWithdraw/NftWithdraw/MtWithdraw (verified against the pinned defuse-core source) carry an optional storage_deposit field -- an unconditional, unrefundable wNEAR debit alongside the withdraw -- and an optional msg field that switches the call into its _transfer_call form. Neither was rendered: a user signing "withdraw 1 wNEAR" could be authorizing an additional, invisible debit of arbitrary size with zero indication.

Fixed: both fields now render on all three withdraw renderers via a shared helper, with new regression tests (*_renders_storage_deposit_and_message, ft_withdraw_omits_message_and_storage_deposit_when_absent) covering both presence and absence.

Verification

• cargo test -p visualsign-near -- 45/45 pass, under both default and --features diagnostics.
• cargo clippy -p visualsign-near --all-targets -- -D warnings, cargo fmt --check -- clean.
• cargo check/clippy -p parser_app --no-default-features --features near -- clean (narrow-build variant).
• make -C src lint, make -C src test -- clean (default features; stock builds unaffected).
• Internal code review and security review both run against this diff; the one finding (storage_deposit/msg) is fixed above with test coverage.

[Copilot]

Pull request overview

Adds NEAR Intents support to visualsign-near by introducing an intents “preset” (decode + render) and merging the crate’s previously separate input-format handling into a single NearTransaction enum that discriminates between on-chain borsh transactions and pre-signature intents JSON envelopes.

Changes:

• Introduces presets::intents with JSON args decoding, token metadata/formatting, rendering for supported intent variants, and partial signature verification plumbing.
• Merges NEAR parsing into NearTransaction::{OnChain, Intent} and updates the converter to dispatch/render accordingly (including execute_intents decoding for intents.near).
• Adds crate feature wiring for diagnostics passthrough (visualsign/diagnostics) and updates tests to cover the new paths.

Reviewed changes

Copilot reviewed 10 out of 11 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/chain_parsers/visualsign-near/src/tx.rs	Parses either borsh NEAR transactions or validates/stores DefusePayload JSON for intent signing flows.
src/chain_parsers/visualsign-near/src/convert.rs	Dispatches conversion based on NearTransaction variant and decodes/renders execute_intents calls.
src/chain_parsers/visualsign-near/src/lib.rs	Exposes the new presets module.
src/chain_parsers/visualsign-near/src/presets/mod.rs	Adds the presets module root and exports intents.
src/chain_parsers/visualsign-near/src/presets/intents/mod.rs	Defines the intents preset API, registry types, errors, and integration tests.
src/chain_parsers/visualsign-near/src/presets/intents/args.rs	Deserializes execute_intents JSON args into MultiPayload list.
src/chain_parsers/visualsign-near/src/presets/intents/render.rs	Renders intents, envelope fields, and signature status into VisualSign fields.
src/chain_parsers/visualsign-near/src/presets/intents/tokens.rs	Provides seeded NEP-141 token metadata and unit formatting helpers.
src/chain_parsers/visualsign-near/src/presets/intents/verify.rs	Adds signature verification + payload extraction helpers (partial, used by rendering).
src/chain_parsers/visualsign-near/Cargo.toml	Adds thiserror and introduces a diagnostics feature wired to visualsign/diagnostics.
src/Cargo.lock	Pulls in thiserror resolution for the NEAR crate.

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