Explain Transaction crates API + improve TypeScript SDK docs

Feedback:

- Suggested adding more natural language explanations for the Transaction crates API (e.g. what the transaction APIs actually do, not just the signatures).
- Documentation is still in progress, but more in-depth examples for the TypeScript SDK would help a lot.
- Suggested having all docs in one place (currently hopping repo to repo feels messy).

Ask:

- Add clearer, higher-level explanations + examples for the Transaction crates API.
- Expand TypeScript SDK docs with deeper examples.
- Consolidate docs into one central place for easier navigation.

Why:
Makes the dev experience smoother and reduces friction when learning the stack.

**This feedback came through DevRel applications.**