fix: validate help module selections

[vycdev2]

Summary

• Validate help-module component selections before parsing page and module data.
• Return a friendly recovery embed instead of throwing on malformed interaction data.
• Add focused coverage for valid and malformed selection identifiers.

Verification

• dotnet restore
• dotnet build --no-restore
• dotnet test Morpheus.Tests/Morpheus.Tests.csproj --no-restore --filter FullyQualifiedName~HelpCommandRegistrationTests
• Full suite: 304 passed, 2 known globalization-invariant baseline failures in NormalizeTimeUntilEventName_NormalizesCase because tr-TR is unavailable in this environment.
• git diff --check passed.
• Repository-wide dotnet format remains blocked by pre-existing line-ending/whitespace findings across the checkout.

This was generated by an AI agent (vycdev2). Please verify any changes before merging or applying.

[vycdev]

Two malformed interaction cases still need coverage before this is safe to merge:

• messageComponent.Data.Values.First() still throws when Discord supplies no selected value. Please use FirstOrDefault() (and allow the parser/recovery path to handle null) or validate the collection before reading it.
• TryParseHelpModuleName accepts values such as 2147483647_StocksModule. Later, (page - 1) * HelpPageSize overflows to a negative index and visibleCommands[i] throws. Please calculate the start index without overflow and reject pages outside the selected module's actual page range.

Please add regression tests for an absent selection and an overflowing/out-of-range page. The current branch otherwise integrates cleanly with develop; its existing focused tests and the full 388-test suite pass.

[vycdev2]

Addressed the malformed interaction cases and rebased onto current develop in 0524c44:

• empty selections now use FirstOrDefault() and flow to the invalid-page response; page bounds use overflow-safe arithmetic and reject pages beyond the selected module’s visible command count; regression coverage includes null selection, out-of-range pages, and int.MaxValue.

Verification: dotnet build passed; focused help tests passed 13/13; full suite passed 440 with 1 skipped; git diff --check passed.

This was generated by an AI agent (vycdev2). Please verify any changes before merging or applying.