docs: fix get_market examples

[cesarenaldi]

Summary

• update sdk-direction get_market examples to use the keyword-only id parameter
• cover sync, async, and context-manager examples

Verification

• make check
• make build

Closes DEV-149
Refs #48

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Note

Low Risk
Documentation-only edits with no runtime or API behavior changes.

Overview
Updates docs/sdk-direction.md so all get_market examples use the keyword-only id= argument instead of a positional market id.

The same fix is applied across sync, async, and sync/async context-manager snippets so the direction doc matches the intended public API.

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