Migrate timegrass to Calcit 0.27 and COS CDN

[tiye]

Summary

• upgrade Calcit and @calcit/procs to 0.27.0 and refresh the full Caps dependency graph
• migrate 100 legacy Option/Result constructor calls to current nominal constructors and replace Option equality with explicit matching
• adapt generated-JavaScript contract tests to Calcit 0.27 reachable-entry emission
• add PR/main/branch COS prefixes, absolute CDN build paths, local and remote asset verification, and fork-safe upload guards
• pin all workflow actions and retain the existing main-only web/server rsync deploys after public CDN verification

Validation

• strict workflow verification for default and server entries
• 14 client tests and 90 server/native tests
• generated-JS dayjs, title contract, session message, and typed database checks
• deprecated API findings: 0 for both entries
• unresolved dynamic method findings: 0 for both entries
• Node 24 / Yarn 4.18 immutable install
• CDN-prefixed Vite build and local asset verification