## Summary

Updates Zed trial copy for
[CLO-1373](https://linear.app/zed-industries/issue/CLO-1373/update-zed-to-show-the-dollar5-gpt-luna-trial).

- Show $5 of GPT Luna and unlimited edit predictions across pre-sign-in,
Free-plan, and active-trial onboarding.
- Clarify that the 14 days begin when the trial starts, rather than when
the welcome panel is viewed, and retain no-credit-card messaging.
- Update hosted-model trial descriptions and use "Start Free Trial" for
onboarding and AI configuration trial CTAs.
- Document GPT Luna-only trial hosted-model access and the shared
Zed/Delta $5 trial balance.

This is a copy-only change. Trial eligibility, subscription creation,
trial timing, billing, model-access enforcement, button actions, URLs,
and telemetry are unchanged. Paid, Student, Business, and VIP plan
descriptions are unchanged. This does not implement the offer on the
backend.

## Verification

- Rust formatting and `git diff --check` passed.
- Prettier check passed for the pricing documentation.
- Source checks confirmed the offer wording and unchanged callbacks,
URLs, telemetry, and other plan definitions.
- Katie built and launched Zed with `cargo run -p zed --bin zed`, then
reviewed Component Preview and requested the final CTA wording.
Formatting and diff checks were rerun after that wording adjustment; the
final adjustment has not been rebuilt.
- Confirmed the branch merges cleanly with the latest `main`.

Release Notes:

- Improved trial descriptions to show $5 of GPT Luna and unlimited edit
predictions for 14 days from trial start.