docs: Clarify that Promptless analyzes only PR diffs, not entire codebases

[promptless]

Adds explicit clarification that Promptless only analyzes changed files in PR diffs, not entire repositories. This addresses customer confusion about the scope of analysis.

Changes:

1. Triggers page: New "What Gets Analyzed" section explaining Promptless only analyzes changed files in the PR diff
2. FAQ page: New question "Does Promptless analyze my entire codebase?" with clear answer about focused PR diff analysis

This helps prevent misunderstandings about Promptless being a code search tool and clarifies the targeted analysis approach.

Trigger Events

• Internal discussion about project setup in Basis, doc analysis for subdirectories, and clarifying Promptless functionality with Capillary team.

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[github-actions]

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