feat(signing): Tron/TON/Solana message signing via vault REST (firmware 7.14.1+)

[BitHighlander]

Summary

Wires the 5 message-signing endpoints landed in vault commit 7e6dfc9:

Endpoint	Purpose
POST /tron/sign-message	TIP-191 personal_sign
POST /tron/verify-message	TIP-191 verify (off-device)
POST /tron/sign-typed-hash	TIP-712 hash mode
POST /ton/sign-message	bare Ed25519 (AdvancedMode-gated)
POST /solana/sign-offchain-message	domain-separated envelope

Replaces the not yet supported throw at tronHandler.ts:702 and adds parallel surfaces on TON and Solana.

Firmware gate

New chrome-extension/src/background/firmware.ts enforces a 7.14.1 minimum on every new method. 7.14.0 was an internal stop-gap that never shipped publicly — treat it as nonexistent so anyone on it sees a clean upgrade prompt instead of a Failure_UnknownMessage round-trip. Same prompt for 7.13.x and earlier.

Per-chain notes

Tron

• tronWeb.trx.signMessage (V1, hex) and tronWeb.trx.signMessageV2 (V2, UTF-8) now route to the backend instead of throwing — only the wire encoding of the message bytes differs between V1 and V2.
• tron_verifyMessage is reachable only via tronLink.request({ method: 'tron_verifyMessage', params: [{ address, signature, message, isText? }] }). We deliberately do NOT expose verifyMessage / verifyMessageV2 on tronWeb.trx: TronWeb V2's contract is verifyMessageV2(message, sig) returning the recovered base58 address, and our endpoint shape (address required, boolean returned) doesn't match. Verification is client-side anyway — TronWeb's static utilities cover it.
• tron_signTypedHash is hash-only. Caller pre-computes the two 32-byte hashes per the TIP-712 spec and passes them in. We do NOT ship a struct → hash implementation, so we do NOT expose _signTypedData / signTypedData on tronWeb.trx where the contract takes (domain, types, value).

TON — Firmware fences ton_signMessage behind the AdvancedMode policy. When disabled, the vault returns a 4xx with AdvancedMode in the body; the handler rewrites that into an actionable prompt (Open Vault → Settings → Security and enable Advanced Mode).

Solana — solana_signOffchainMessage is a NEW method exposed to dApps via a vendor-namespaced Wallet Standard feature, keepkey:signOffchainMessage. dApps feature-detect:

const f = wallet.features['keepkey:signOffchainMessage'];
if (f) await f.signOffchainMessage({ message, version, messageFormat });

solana_signMessage (Wallet Standard bare-message) is unchanged. The signature returned by the off-chain method is over the envelope:

"\xff" || "solana offchain" || version (1B) || format (1B) || length (2B LE) || message

Verifiers MUST reconstruct the envelope and Ed25519-verify against THAT, not the bare bytes. The approval event carries a verifyAgainst: 'envelope' hint for any future approval-card UI. Defaults: version 0, messageFormat 1 (UTF-8); 1212-byte cap matches firmware.

Test plan

• Tron: tronWeb.trx.signMessageV2('hello') from a dApp prompts approval and returns a 0x-prefixed 65-byte signature
• Tron: tronWeb.trx.signMessage('0xdeadbeef') (V1, hex) prompts approval and returns a 0x-prefixed 65-byte signature
• Tron: tronLink.request({ method: 'tron_verifyMessage', params: [{ address, signature, message, isText: true }] }) returns true for a valid round-trip and false for a tampered message
• Tron: tronLink.request({ method: 'tron_signTypedHash', params: [{ domainSeparatorHash, messageHash }] }) with two 32-byte hex hashes signs and returns a recoverable signature
• Tron: confirm tronWeb.trx._signTypedData and tronWeb.trx.verifyMessageV2 are intentionally absent (no compat claim)
• TON: ton_signMessage with AdvancedMode disabled surfaces the "enable Advanced Mode" prompt (no opaque 4xx)
• TON: ton_signMessage with AdvancedMode enabled signs and returns { publicKey, signature }
• Solana: wallet.features['keepkey:signOffchainMessage'].signOffchainMessage({ message: 'hello' }) returns { publicKey, signature }; verifying against the bare message FAILS, verifying against the reconstructed envelope succeeds
• Firmware 7.14.0 device hits the upgrade prompt for all 5 methods (manual: temporarily downgrade or hardcode)
• Type-check + build clean (verified locally; CI lint failure is pre-existing repo debt, out of scope)

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