docs: clarify OrkesClients works with OSS Conductor, no account required

[nthmost-orkes]

Summary

• Added a callout note after the quickstart Run it: block explaining that OrkesClients works with self-hosted OSS Conductor and requires no Orkes account
• Added # works with OSS Conductor and Orkes Conductor comment to the second OrkesClients import in the Feature Showcase section (first import already had this comment)

User impact: First-time OSS users following the quickstart saw a class named OrkesClients and reasonably wondered if they needed an Orkes account or paid service. Now there's a visible note right where they're most likely to pause — immediately after running the app — making it clear the name reflects the implementing org, not a cloud requirement.

Closes conductor-oss/getting-started#45 (doc-only fix; the ConductorClients alias discussed in that issue remains open as a separate low-priority enhancement).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
see 57 files with indirect coverage changes

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