build: upgrade SwiftFormat to 0.58.7

[robmaceachern]

Summary

Upgrade the mise SwiftFormat pin from 0.55.0 to 0.58.7 to support Swift 6.2 raw identifiers, including human-readable Swift Testing function names.

This one-line, main-based tooling PR supports MRKT-142 and can land independently of navigation/content-lifecycle changes. The formatter configuration, Swift sources, package dependencies, and CI workflow are unchanged. Keep this PR draft until Rob manually examines it and explicitly approves conversion; no automatic readiness conversion or merge.

Validation

• mise exec -- swiftformat --version reports 0.58.7.
• mise exec -- swiftformat --lint . --cache ignore: 0/140 files require formatting; six files skipped by formatter/configuration rules. The unchanged source tree also passed the previous 0.55.0 formatter.
• A standalone Swift Testing fixture with a backticked, space-containing function name fails the old parser and passes lint under 0.58.7 with this repository's configuration and Swift 6.0.2 formatting mode.
• git diff --check passes. Runtime tests were not rerun locally for a formatter-pin-only change.

Checklist

• Unit Tests
• Documentation (scope and validation documented above; no API documentation changes needed)
• Pull request title follows conventional commits

---

This response was drafted with AI assistance.