docs: clarify TON signData support boundaries

[cursor]

Summary

• document the new tonSignData TON Connect flow in docs/chain.md
• clarify in docs/device-method-support.md that the device compatibility matrix only reflects declared overrides
• note that tonSignData is wired in SDK and playground examples but is not yet part of the verified device compatibility matrix

Codepaths covered

• packages/core/src/api/ton/TonSignData.ts
• packages/core/src/types/api/tonSignData.ts
• packages/hd-transport/src/types/messages.ts
• packages/connect-examples/expo-example/src/data/ton.ts
• packages/connect-examples/expo-example/src/testTools/deviceCompatibility/plugins/*.ts

Gaps addressed

• missing public interface docs for tonSignData
• unclear support boundary between SDK wiring and device-level compatibility verification

  

[revan-zhang]

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