fix: add leading space to generated field doc comments (#5)

## Summary

- Adds a leading space to the `format!()` strings that produce `#[doc =
...]` attributes in the codegen, so prettyplease renders them as `///
Field ...` instead of `///Field ...`
- Three one-character changes across `message.rs` (line 1057) and
`view.rs` (lines 312, 322)

Fixes #4

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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Co-authored-by: alexchenai <alexchenai@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Co-authored-by: Iain McGinniss <309153+iainmcgin@users.noreply.github.com>

Author: 3 people