fix(settings): prevent WebUI save status wrapping

[su-fen]

Linked issue

Closes #465

Summary

Prevent the Gateway WebUI settings save-status indicator from wrapping Chinese text between characters when horizontal space is constrained.

The indicator and its status dot now keep their intrinsic width, while the save-status text remains on one line.

Change scope

• Modules: agent-ui / Gateway WebUI settings
• Key paths: crates/agent-ui/src/pages/settings/SettingsShell.tsx

Screenshots / preview

Verification

• cd crates/agent-ui && pnpm exec biome check src/pages/settings/SettingsShell.tsx --diagnostic-level=error --max-diagnostics=20
• pnpm check:ui-boundaries
• cd crates/agent-gateway/web && pnpm build
• cd crates/agent-gui && pnpm build
• git diff --check

Pre-submit checklist

• A requirement issue is linked.
• Synced with the target branch; no merge conflicts.
• The change is focused, with no unrelated modifications.
• No secrets, tokens, or personal data included.
• Docs are not required for this localized layout correction.
• Before/after screenshots are attached before marking the PR ready for review.