CS-2 Staging stays inside the claim

In a checkout that other sessions share, nothing that stages for a commit, whether the agent, a hook or a stage line a tool prints, SHOULD stage a path outside the session's claim.

Field	Value
Keyword	SHOULD
Level	2
Checked	by judgement
Findings	F201, F200
Harness facts	none
Threat	construct: an incident nobody filed leaves no trace, so whether the remedies worked is unknown
Status	active

Rationale: F201 (R2/S2) records three routes by which one session's commit took another's work in roadkeep: a commit staged beyond its task, a hook that staged a whole file, and a stage line the tool printed that named a file both sessions had touched. Only the first is the agent's own staging, so the rule covers every stager, not the agent alone. A stage-everything tool is outside the claim by construction (F200), which is why CD-3 in CD.md allows it only where one session owns the checkout. Staging by path does not separate two sessions that edit the same file, as roadkeep's own rationale for the remedy notes and a later incident showed (F201); that case is an open question.