[codex] fix dragged event duration collapse

[Uarmagan]

Summary

• Preserve an event's existing duration when the first drag movement happens before drag metadata is initialized.
• Add a small regression test for the drag-duration fallback.

Root cause

The first drag update could run before drag status had recorded the event duration. The old fallback used 0 minutes, so the event could be saved with a collapsed end time. The UI then rendered it as a tiny event when the week was reloaded, which also triggered the small-event font size.

Validation

• NODE_ENV=test TZ=Etc/UTC bun test src/views/Calendar/components/Draft/hooks/actions/useDraftActions.test.ts src/views/Calendar/components/Draft/hooks/effects/useDraftEffects.test.ts src/views/Calendar/components/Draft/hooks/actions/submit.parser.test.ts
• bunx biome check packages/web/src/views/Calendar/components/Draft/hooks/actions/drag-duration.util.ts packages/web/src/views/Calendar/components/Draft/hooks/actions/useDraftActions.test.ts packages/web/src/views/Calendar/components/Draft/hooks/effects/useDraftEffects.test.ts
• bun run test:web
• bun run lint (passes with existing repo warnings)

Notes

• bun run type-check currently fails on origin/main with tsconfig.json(62,27): error TS5103: Invalid value for --ignoreDeprecations; this PR does not change that config.

Closes #1698