Adopt the Fleet code-health quality gate

[sarthakagrawal927]

Summary

• add required mixed web/native code-health gates for coverage, unused code, complexity, duplication, cycles, dependency risk, suppressions, formatting, and repository hygiene
• normalize the existing web/Worker source to the new formatter baseline and remove unused public exports
• add portable simulator selection, native test/Release validation, and whole-production Swift coverage to CI
• conservatively update development tooling only; production dependencies are unchanged

Evidence

• pnpm quality
• pnpm quality:native
• cleanup receipt run_669cade644da2a42ad7eace42d993dd8

Accepted debt

Tracked in #28. New regressions fail the gate; exact accepted dependency advisory IDs are pinned.

Closes #27