Enhance staffing management with uncovered teacher tracking

- Updated `protocol.md` to clarify the concept of uncovered subjects and the number of additional teachers required.
- Introduced `teachersShort` property in the `StaffingSubject` interface to indicate how many more teachers are needed for a subject.
- Enhanced localization strings to reflect the new uncovered teacher information in both English and Russian.
- Updated the management panel UI to display the number of teachers short for each uncovered subject.
- Revised the `Uncovered` method in the staffing logic to return detailed information about uncovered subjects, including the shortfall of teachers.
- Added tests to validate the new uncovered teacher tracking functionality and ensure accurate reporting in the staffing API.
- Marked related tasks as complete in the documentation for the golden fixtures phase.

tests/HSchool.People.Tests/golden/README.md

@@ -0,0 +1,14 @@
+# Golden roster
+
+`roster.txt` is the fingerprint of `RosterGenerator` for a fixed seed, four classrooms, Slavic
+names and Russian as the native language.
+
+Update it **in the same commit that changes generation**, and say in the commit message what
+changed (a new skill, a related-language roll, a different birth window). A red golden test is
+the question "did you mean to?", not an order to revert.
+
+To rewrite the file after an intentional change:
+
+```
+WRITE_GOLDEN=1 dotnet test tests/HSchool.People.Tests/HSchool.People.Tests.csproj --filter GoldenRoster_MatchesFixture
+```