docs: Explain non-blocking provider registration

[kinyoklion]

The OpenFeature Python SDK 0.10.0 made api.set_provider non-blocking and added api.set_provider_and_wait, which changes when an application can rely on initialization having completed.

• README usage section now explains that set_provider returns before initialization finishes, so early evaluations may fall back
• Points applications that need to block at set_provider_and_wait

Requirements

• I have added test coverage for new or changed functionality (documentation only)
• I have followed the repository's pull request submission guidelines
• I have validated my changes against all supported platform versions

Related issues

None.

Implementation details

Verified in openfeature/api.py of the Python SDK: set_provider registers without wait_for_init, while set_provider_and_wait passes wait_for_init=True. The provider's supported range (openfeature-sdk >=0.9.0,<1) includes releases with both behaviors, so the note describes the current SDK behavior rather than a provider change.

No behavior change; documentation only. The paragraph sits next to the start_wait discussion, so this may need a trivial rebase alongside the open start_wait PR.

Link to Devin session: https://app.devin.ai/sessions/a47abf28ecd44130917b9b5131287221
Open in Devin Desktop: https://app.devin.ai/desktop/session/a47abf28ecd44130917b9b5131287221?variant=devin
Requested by: @kinyoklion

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Note

Overview
Documents how OpenFeature Python SDK provider registration behaves after set_provider became non-blocking in SDK 0.10.0.

The README Usage section adds a short note after the start_wait explanation: api.set_provider returns before the LaunchDarkly provider finishes initializing, so early flag evaluations may see fallback values while the client connects. Apps that must not evaluate until init completes are directed to api.set_provider_and_wait.

No runtime or provider code changes—documentation only.

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