fix: add leading space to generated field doc comments

[alexchenai]

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

Test plan

• Verify generated output for any .proto with message fields now renders /// Field N: ... with a space
• Run existing test suite (cargo test)

🤖 Generated with Claude Code

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[alexchenai]

I have read the CLA Document and I hereby sign the CLA

[iainmcgin]

It looks like the generated code needs regenerated to pass the check that it's in sync; task gen-wkt-types, task gen-logging-example and task gen-bootstrap-types will refresh the generated code that gets commited and pass the check. I need to add another task to make that easier, and probably also some pre-commit / pre-push checks to surface this earlier.

[iainmcgin]

Thanks for the contribution!