Session Handoff [auto-1633]: Stop Crediting an until read Loop as Bounded in the Guard per #1633 #2159

Next steps, in priority order

1. Fix An until read Loop Over an Exhausted Input Passes Requirement 7 #1633 in host-setup/agent-safety/claude/gh-write-guard.py. Requirement 7's read bound credits a loop whose condition is a leading read on a descriptor-0 redirect without telling while from until. For until, an exhausted or empty input keeps the condition false forever, so the loop never ends. Stop crediting a read condition as a bound on an until loop, and leave the while case exactly as it is. Done looks like: until read l; do sleep 30; done < f is denied by _unbounded_wait_loop, while read l; do sleep 30; done < f is still allowed, and the suite carries both as cases beside the existing requirement 7 cases.
2. Correct the two statements An until read Loop Over an Exhausted Input Passes Requirement 7 #1633 names as false, _reads_its_input's docstring ("a read, which ends the loop when the input is exhausted") and host-setup/agent-safety/README.md requirement 7 ("which is bounded by that input"), so each says the bound holds for a while loop only. Keep the wording to that one fact.
3. Drive the pull request to develop with Closes on promotion: #1633 in its body, per the unattended-handoff worker procedure, then close this lane out.

External blockers

None known at creation. No open decision issue names #1633.

Internal dependencies

• Step 2 follows step 1, since the corrected wording describes the behavior step 1 settles.
• Other lanes hold unmerged work in the same file: the open PR Deny a Signal-0 timeout as a Wait Bound in the Guard #2117 (lane auto-1634) and the parked branches of lanes auto-2080 and auto-2112. Branch from current develop and expect a rebase conflict for whichever of those lands second, rather than building on any of their branches.

State

• Created by an unattended-handoff picker, scope develop. No branch, worktree, or pull request exists for this lane yet.
• Measured on develop at creation: _unbounded_wait_loop returns no loop (allowed) for both until read l; do sleep 30; done < f and while read l; do sleep 30; done < f, and returns the loop (denied) for until [ -f x ]; do sleep 30; done. Re-measure before editing.

The parked decision queue

Nothing parked on this lane. The repository's open decision issues each belong to another lane.

What the last round did

Picked #1633 from the open backlog as auto-resolvable: the issue states one outcome, carries no decision, blocked, or handoff label, has no comment, stays inside this repository's tree, and no pull request, handoff, or earlier auto-1633 link names it.

What not to repeat

• Three other guard lanes parked on their review budget (Decision: How the Guard Reads a Shell-Rewritable Word in a timeout Run (#2117) #2118, Decision: Whether the #2112 Heredoc Fix Ships With Three Open Review Findings #2126, Decide How the #2080 eval Fix Continues Past Its Review Budget #2139), each after restating a parser's scope in prose. Keep the docstring and README change to the single while-only fact rather than re-describing the whole bound.

New learnings

None yet.