Label individual and pair assignments; make starter optional

[zhongnz]

Problem and result

The common [Cohort] prefix did not show whether each student or each pair owed the output. Use [Individual assignment] and [Pair assignment] titles with matching filter labels; keep [Individual] personal tasks and [Pair] case records distinct. Optional examples/help use [Resource].

Make starter practice optional throughout the student guide, README, task map, semester plan, grading guidance, walkthrough and forms. It has no required submission, deadline or grade penalty. Foundation can be fully demonstrated with other substantive evidence, and previous starter work retains credit. Onboarding can use a browser roster PR without Git, Python or a starter run. The tentative 75/25 weights and case research requirements stay intact.

Completed live synchronization

• Classified the existing assignment guides and added individual-assignment, pair-assignment and optional labels.
• Updated [Individual assignment] Optional starter practice #1/[Pair assignment] Register your pair and case #3/[Individual assignment] Onboarding and roster entry #5/[Resource] Optional examples and setup help #6 and course notes [Course] Working arrangements and adjustments #24 to reflect optional practice; updated M1's description without changing its date.
• Removed M1 from starter [Individual assignment] Optional starter practice #1 and personal starter task [Individual] katsukii — Starter reproduction and critique #30. Preserved [Individual] katsukii — Starter reproduction and critique #30's original record verbatim beneath a dated maintainer clarification, kept its owner/review request, and added optional. No contribution or completion is invented.
• Verified 14 live issue updates, M1 description, unchanged issue states/owners and milestone dates, and all three new label filters against the intended mapping.

Validation

• Documentation links/anchors, form YAML and grading arithmetic pass.
• Checked the proposed live changes, assignment categories, absence of a starter deadline, and preservation of student evidence.
• git diff --check passes. Required Python 3.11/3.13 CI passed; engine and test behavior are unchanged.

Merge handling

The repository owner remains the sole eligible reviewer. Used the documented owner bootstrap exception after required checks passed on b5fce73eafb421dbd775c0451214c56f25f1cc6f. No independent approval or formal course grading approval is implied.

Merged main at cf5bfc87e9d5de6f46a0c661dd52182d1bd1c0bd also passed CI. Local main is clean and synchronized.