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🤖 This is an automated PR from Repo Assist, an AI assistant for this repository.

Summary

FindRelatedSections previously searched every site mapping for each semantic result. This change builds a per-request chapter/heading index once and uses dictionary lookups, reducing the mapping phase from O(results × mappings) to O(mappings + results) while preserving case-insensitive matching and first-match behavior.

Root cause and rationale

Related-section results performed a linear scan of the complete site-mapping collection for every result. As the book mapping grows, that repeated work scales unnecessarily. The local index keeps the existing result and fallback behavior but avoids repeated enumeration.

Test Status

• ✅ dotnet build EssentialCSharp.Web/EssentialCSharp.Web.csproj --configuration Release --no-restore
• ⚠️ dotnet test EssentialCSharp.Web.Tests/EssentialCSharp.Web.Tests.csproj --configuration Release --no-restore: 149 passed, 2 pre-existing external integration failures (CaptchaService_Verify_Success and KnownBreachedPassword_IsDetected) because their third-party services were unavailable in this environment.
• ✅ git diff --check

No new dependencies were added.

Warning

Firewall blocked 2 domains

The following domains were blocked by the firewall during workflow execution:

• api.hcaptcha.com
• api.pwnedpasswords.com

To allow these domains, add them to the network.allowed list in your workflow frontmatter:

network:
  allowed:
    - defaults
    - "api.hcaptcha.com"
    - "api.pwnedpasswords.com"

See Network Configuration for more information.

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[Copilot]

🟢 Approval recommended

The localized optimization preserves existing lookup behavior, with no unresolved findings.

No open issues 🎉

What changed in this PR

Optimizes related-section mapping in FindRelatedSections by replacing repeated scans with a per-request index.

Changes:

• Indexes site mappings by chapter and heading.
• Uses dictionary lookups while preserving case-insensitive matching, first-match selection, and fallback behavior.

File	Description
EssentialCSharp.Web/​Tools/​BookSearchTool.cs	Replaces repeated mapping scans with indexed lookups.

_{Review effort: Balanced}

[Copilot]

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