Keep teleprompter speed readouts in the selected display mode

[KSemenenko]

Problem

The Teleprompter reader speed display mode can be switched between WPM and multiplier labels, but the lower transport speed readout can remain in WPM while other reader speed labels use multipliers. That makes the reader inconsistent after changing the display mode.

Acceptance criteria

• Switching the Teleprompter reader speed display mode to multiplier updates every reader speed readout, including the bottom transport speed label.
• Switching back to WPM keeps the same consistency across reader speed readouts.
• The multiplier is calculated from the script/base TPS WPM and the active reader playback WPM.
• Component and browser UI coverage prove the transport label follows the selected speed display mode.

Verification expected

• dotnet test @./tests/dotnet-test-progress.rsp --project ./tests/PrompterOne.Web.Tests/PrompterOne.Web.Tests.csproj
• dotnet test @./tests/dotnet-test-progress.rsp --project ./tests/PrompterOne.Web.UITests.Reader/PrompterOne.Web.UITests.Reader.csproj

[KSemenenko]

Implemented in local commit 982d9bb.

What changed:

• The bottom Teleprompter transport speed label now follows the selected reader speed display mode.
• When the reader is in multiplier mode, the transport speed label uses the same base TPS WPM multiplier calculation as the rest of the reader speed UI.
• Added component and browser UI coverage so the multiplier toggle proves the lower speed label changes too.
• Added the consistency rule to src/PrompterOne.Shared/AGENTS.md so future Teleprompter speed readouts do not diverge again.

Validation:

• dotnet format ./PrompterOne.slnx --include src/PrompterOne.Shared/Teleprompter/Pages/TeleprompterPage.ReaderRendering.cs tests/PrompterOne.Web.Tests/Teleprompter/TeleprompterPersistenceTests.cs tests/PrompterOne.Web.UITests.Reader/Teleprompter/TeleprompterSettingsFlowTests.cs
• dotnet test @./tests/dotnet-test-progress.rsp --project ./tests/PrompterOne.Web.Tests/PrompterOne.Web.Tests.csproj - passed, 629/629
• dotnet test @./tests/dotnet-test-progress.rsp --project ./tests/PrompterOne.Web.UITests.Reader/PrompterOne.Web.UITests.Reader.csproj - passed, 176/176
• dotnet test @./tests/dotnet-test-progress.rsp --solution ./PrompterOne.slnx - passed, 1191/1191
• dotnet publish ./src/PrompterOne.Web/PrompterOne.Web.csproj -c Release -o ./artifacts/publish/PrompterOne.Web - passed

Ready for verification. After the release that includes this commit is cut, add the app version/build number here before closing.