docs: add documentation for Stellar contracts and Wraith names regist…

[emarkees]

Closes #24

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## Description

This PR introduces comprehensive documentation for the `.wraith` names lifecycle on Stellar. It acts as the definitive guide for registering, managing, and resolving stealth identity meta-addresses across the Wraith Protocol, complete with SDK and CLI examples. 

## Changes Made

- New Guide (`docs/guides/wraith-names-stellar.mdx`):
  - Outlines the 3-32 lowercase alphanumeric naming rules.
  - Documents the full identity lifecycle with both TypeScript SDK and `soroban` CLI examples: `register`, `update`, `release`, `resolve`, and `name_of`.
  - Explains Stellar-specific constraints, including Friendbot funding for testnet, minimum balance requirements on mainnet, and mempool front-running considerations.
  - Documents gasless/on-behalf registrations using Soroban's delegated auth framework.
  - Explains privacy implications, specifically detailing that name registrations are public but the payments utilizing them remain completely private.
  - Prepares the documentation for the upcoming Subdomain Delegation feature (e.g., `payments.alice.wraith`), currently gated behind an upcoming release note.
  
- **Navigation & Configuration Updates (`docs.json`)**:
  - Added the new guide to the sidebar under the `Operations` group within the `Guides` tab.
  - Fixed a pre-existing syntax error (missing comma and formatting) in the `docs.json` navigation array.

- **Cross-Referencing**:
  - **`sdk/chains/stellar.mdx`**: Added a link pointing to the new guide in the `See Also` section.
  - **`contracts/stellar.mdx`**: Inserted a contextual note and link to the guide under the `wraith-names` contract overview section.

## Verification
- Verified all markdown and MDX component syntax.
- Confirmed navigation rendering and fixed missing comma bug in `docs.json`.
- Verified Soroban CLI commands against standard Stellar SDK and CLI testnet usage.

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[truthixify]

Same-day delivery! 216-line wraith-names guide + contract reference cross-link + sdk page touch. Thanks @emarkees.