Clarify case choices and research collaboration across pairs

[zhongnz]

Summary

Students need concrete starting questions and a clear way to share research across pairs. This focused documentation update expands the case guide to seven optional workflow ideas, each with a bounded question and an evidence route to check. Multiple pairs may study the same workflow through complementary questions or deliberate replication.

• Add a resource-selection table and a small feasibility check that can be recorded in an existing task.
• Explain when shared experiments are comparable, how to account for reused evidence, and how to preserve each student's contribution credit.
• Add a short question/finding field to the existing report index, reusing case-report wording at registration and handoff.

The four-document change preserves the broad research scope, optional propagation/starter practice, tentative 75/25 grading, current working dates, and existing Pair case/Individual task workflow. It adds no platform dependency or student submission. External environments and trace sources remain candidates requiring actual access/setup checks.

Relates to #3, #6, #9, and #24; these cohort collections remain open.

Validation and attribution

• Checked 179 local Markdown links and anchors across all 24 tracked Markdown documents.
• git diff --check passed.
• Compared the guidance with the research plan, student guide, grading, semester plan, issue forms, and resource/course collection issues.
• Required Python 3.11/3.13 unit tests and pilot smoke runs passed on final revision 007a71b6aade35f7b061b1b899b3bd134117dde9: PR CI run.

Maintainer documentation work prepared and checked with Codex assistance; no student work or empirical results are claimed.

Merge review

The owner's September 25 instruction authorizes modest repository improvements. The GitHub API confirms that zhongnz is the only eligible collaborator/code owner, so this owner-authored PR cannot obtain independent approval. Required checks passed before the merge used the documented owner bootstrap exception in CONTRIBUTING.md and the access guide. Preserve the merge commit and existing protections; this exception does not represent an independent review.