fix(desktop): use sentence case in trace

[Phoenix500526]

Summary

Normalize the Time breakdown labels to sentence case so they match the
adjacent Token usage labels.

• Recorded Time becomes Recorded time
• LLM Calls becomes LLM calls
• Tool Runs becomes Tool runs

Verification

• npm exec -- biome check apps/desktop/src/renderer/locales/conversation-copy.ts
• npm --workspace @maka/desktop run typecheck
• Verified the hot-reloaded Trace panel in the actual Desktop; all three labels
  render in sentence case without changing the existing layout
• Automated behavioral tests were not added because this is a copy-only change

Before

After

AI use

Select exactly one:

• No generative tool made a substantive contribution
• Generative tooling made a substantive contribution

Tool(s) and scope: OpenAI Codex assisted with the copy edit, verification,
commit, and PR preparation.

Checklist

• Tests cover the change and fail without it
• Lint, format, typecheck and the affected suites pass locally

Does this PR entail a change in behavior?

• Yes, the English labels now use sentence case
• No