docs(guides): Improve intro paragraph formatting and expand custom spans description

[jaffrepaul]

DESCRIBE YOUR PR

Minor formatting and content improvements across the guides section:

• Split dense opening paragraphs in issues-errors, logs, metrics, querying-traces, and session-replay guides into two sentences for better readability
• Expanded the custom-spans guide intro to clarify what custom spans add (business context, logical groupings, attributes) and note that they often appear as parents of auto-generated child spans

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Project	Deployment	Actions	Updated (UTC)
develop-docs	Ready	Preview, Comment	May 15, 2026 1:31pm
sentry-docs	Ready	Preview, Comment	May 15, 2026 1:31pm

[coolguyzone]

TY for your attention to detail 🫡

[github-actions]

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