feat(vara-eth-api): validating injected tx promise, rename Injected -> InjectedTx

[osipov-mit]

resolves #2255

Added

• InjectedTxPromise class for handling promise replies from injected transactions and validating promise signature

Changed

• Renamed Injected class to InjectedTx (with backward-compatible alias)
• Refactored injected transaction code into separate modules (tx.ts and promise.ts)
• Updated IInjectedTransactionPromise interface: flattened reply structure, changed value from number to bigint, changed code to Hex

[Copilot]

Pull request overview

This PR refactors the injected transaction handling in the vara-eth API by renaming the Injected class to InjectedTx (maintaining backward compatibility) and introducing promise validation functionality. The key improvement is the addition of signature validation for transaction promises returned by validators.

• Introduced InjectedTxPromise class with signature validation capability
• Refactored injected transaction code into separate modules (tx.ts and promise.ts)
• Updated the IInjectedTransactionPromise interface with a flattened structure and proper types

Reviewed changes

Copilot reviewed 13 out of 14 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
apis/vara-eth/test/injected.test.ts	Added tests for promise hash generation, signature validation, and account recovery
apis/vara-eth/src/types/api/injected.ts	Flattened reply structure and changed value type from number to bigint, code to Hex
apis/vara-eth/src/eth/router.ts	Changed validators return type from readonly Hex[] to Address[] for type safety
apis/vara-eth/src/api/injected/tx.ts	Refactored to use new InjectedTxPromise class and updated RPC method names
apis/vara-eth/src/api/injected/promise.ts	New class implementing promise validation with hash computation and signature verification
apis/vara-eth/src/api/injected/index.ts	Added backward-compatible exports with deprecation markers
apis/vara-eth/src/api/index.ts	Updated exports to include new classes
apis/vara-eth/src/api/api.ts	Updated to use renamed InjectedTx class
apis/vara-eth/programs/injected/src/main.rs	Added promise generation logic for testing signature validation
apis/vara-eth/programs/injected/Cargo.toml	Added required dependencies for promise testing
apis/vara-eth/README.md	Updated documentation with promise validation example and deprecation notice
apis/vara-eth/Cargo.toml	Added workspace dependencies for gear-core libraries
apis/vara-eth/Cargo.lock	Updated dependency versions
apis/vara-eth/CHANGELOG.md	Documented new features and breaking changes

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