Recommend service macro

[zeenix]

• ✨ macros: service now allows returning borrowed errors
• 💡 README: Add missing . in sample code comments
• 📝 README: Use & recommend service macro
• 📝 core: Recommend high-level API in Connection docs
• 📝 core: Service recommend use of service macro

Fixes #212.

[codspeed-hq]

Merging this PR will not alter performance

✅ 4 untouched benchmarks

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_{Comparing zeenix:service-in-docs (b5912bd) with main (f35ed2a)}

[Copilot]

Pull request overview

This PR updates the docs and examples across the repo to recommend using the high-level #[service] attribute macro (instead of manually implementing Service), and extends the service macro codegen so it can correctly handle borrowed lifetimes in parameters/returns/errors.

Changes:

• Update service macro codegen to normalize lifetimes for (de)serialization so borrowed types work.
• Add a new macro test covering borrowed lifetimes in return/error types.
• Refresh README + core docs to recommend the proxy/service macros and adjust the main example accordingly.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
zlink-macros/tests/service/borrowed-types.rs	New integration test covering borrowed lifetimes in service return/error types.
zlink-macros/tests/service.rs	Registers the new borrowed-types test module.
zlink-macros/src/service/codegen.rs	Converts lifetimes to synthetic '__de/'__ser to support borrowed types in generated enums.
zlink-core/src/server/service.rs	Adds docs recommending #[service] for implementing Service.
zlink-core/src/connection/mod.rs	Expands module docs to recommend proxy + service macros over the low-level API.
README.md	Updates the public example to use #[proxy]/#[service] and fixes comment punctuation.

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