docs: refresh README discovery

[Faeif]

What changed

• Added a polished editorial cover image and clear project identity.
• Reworked the README around value, five-minute setup, workflow, and team use.
• Restored the complete, expandable list of all 13 skills for prospective users and forkers.

Why

Make CaseKit easier to discover, understand, and adopt from its GitHub landing page.

Validation

• python3 scripts/validate_suite.py

[devin-ai-integration]

Devin Review found 2 potential issues.

[devin-ai-integration]

🔴 The five-minute getting-started instructions fail because the second command refuses to run

The quick-start tells new users to install into the case folder first (python3 install.py --scope project --project-root /path/to/your-case at README.md:42), which creates that folder before the workspace-creation command runs, so the next command aborts with "Refusing to overwrite existing path" and no workspace is ever created.
Impact: Anyone following the headline setup instructions hits an error and cannot create a case workspace.

Why the ordering breaks: init refuses pre-existing destinations and already installs skills itself

cmd_init in casekit.py:170-173 raises SystemExit(f"Refusing to overwrite existing path: {destination}") when the destination exists. install.py --scope project --project-root /path/to/your-case creates /path/to/your-case/.agents and /path/to/your-case/.claude, so the directory exists by the time casekit.py init runs. Reproduced locally: the second command prints Refusing to overwrite existing path.

Additionally the install step is redundant: casekit.py:180 already runs install.py --scope project --project-root <destination> as part of init.

Suggested change

	cd casekit
	python3 install.py --scope project --project-root /path/to/your-case
	python3 casekit.py init /path/to/your-case --layout clean --team "Alice,Bob,Carol"
	```
	cd casekit
	python3 casekit.py init /path/to/your-case --layout clean --team "Alice,Bob,Carol"

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[devin-ai-integration]

🟡 Team setup section names starting files that do not exist in the team layout

The team-workflow section says generated workspaces include README-START-HERE.md and TEAM-WORKFLOW.md (README.md:126), but for the team layout described in that section those two files are deleted and replaced by a single 00-START-HERE.md, so teams look for onboarding files that are not there.
Impact: New teams following the documented team setup cannot find the starting instructions the README points them to.

Clean layout removes both files

apply_clean_layout in casekit.py:135-139 unlinks README-START-HERE.md and TEAM-WORKFLOW.md, then writes clean-layout docs; casekit.py:196 prints 00-START-HERE.md as the starting point for --layout clean, and scripts/validate_suite.py:157-158 asserts 00-START-HERE.md exists in the clean layout.

Suggested change

	This keeps exploration safe: chat output and unconfirmed ideas stay in personal drafts; only a decision or test turns an idea into an official artifact. Generated workspaces include `README-START-HERE.md` and `TEAM-WORKFLOW.md` with the exact workflow.
	This keeps exploration safe: chat output and unconfirmed ideas stay in personal drafts; only a decision or test turns an idea into an official artifact. Team workspaces created with `--layout clean` include `00-START-HERE.md` with the exact workflow.

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