tx: improve JSDoc annotations

[ScottyPoi]

Adds missing JSDoc annotations to functions in the tx package

[Copilot]

Pull Request Overview

This PR enhances code documentation by adding comprehensive JSDoc annotations to utility functions and type guards in the tx package. The changes improve developer experience by documenting function parameters, return types, and behavior.

• Added JSDoc annotations to utility functions in internal.ts
• Added JSDoc annotations to type guard functions in types.ts
• Added JSDoc annotations to capability functions in legacy.ts and eip2718.ts

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
packages/tx/src/util/internal.ts	Added JSDoc annotations for utility functions including getCommon, txTypeBytes, validateNotArray, sharedConstructor, and getBaseJSON
packages/tx/src/types.ts	Added JSDoc annotations for type guard functions checking transaction types and transaction data types
packages/tx/src/capabilities/legacy.ts	Added JSDoc annotations for errorMsg and isSigned helper functions
packages/tx/src/capabilities/eip2718.ts	Added JSDoc annotations for EIP-2718 transaction helper functions including getHashedMessageToSign, serialize, and validateYParity

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.75%. Comparing base (a8e0e8a) to head (d6f27af).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

Flag	Coverage Δ
block	87.58% <ø> (ø)
blockchain	89.37% <ø> (ø)
common	97.43% <ø> (ø)
evm	72.39% <ø> (ø)
mpt	89.69% <ø> (+0.25%)	⬆️
statemanager	80.21% <ø> (ø)
static	99.77% <ø> (ø)
tx	88.23% <ø> (ø)
util	89.77% <ø> (ø)
vm	57.24% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[holgerd77]

Please label.

Also - as a tip: these kind of PRs can be run with the new "type: test no browser" and "type: skip most of VM" labels, then CI is significantly faster.

[holgerd77]

Looks good