Refine FlowChat presentation, session drafts, and usage settings

[GCWing]

Summary

• Add shared thinking indicators, completion handoff, file revision summaries, and Design Lab registration.
• Refine FlowChat group and tool-card presentation, session drafts, workspace selection, and session lifecycle handling.
• Update usage statistics, settings copy, and the corresponding English and Chinese locales.

Validation

• Design-system build, tests, and type checks passed. The typography audit passed after replacing shorthand font declarations in the new preview.
• Web UI appearance and theme contracts passed. Web UI TypeScript passed after supplying ignored generated API bindings locally for validation.
• i18n audit and color audit passed; 140 focused Web UI tests passed.
• Git whitespace and merge-tree checks passed against current main.

Scope and limits

• Excludes the eight modified Markdown guidance/design/process documents from the source checkout.
• No browser or mock-based visual verification was performed. Remote scenarios were not exercised.