Loop: Installer auto-detects binaries for the invoking user, not the configured service_user

[JacobStephens2]

A draft proposal from one unattended Run of the Loop. Nothing here is merged,
deployed, or applied; the Run pushed this branch and opened this pull request,
and that is the whole of what it did outside its own repository.

• Task: Installer auto-detects binaries for the invoking user, not the configured service_user #92
• Owning area this Run was scoped to: Installer auto-detects binaries for the invoking user, not the configured service_user
• Ended by: agent-failed
• Run exit code: 4
• Branch: loop/92-installer-auto-detects-binaries-for-the-invoking, proposed against main

How to review this

Read PROGRESS.md first. It is the narrative of the Run - what each
Iteration did, what it decided and why, and what it found blocked - and the diff
is easier to judge knowing how it was arrived at. PLAN.md carries the
task, its acceptance criteria, and the mechanical check that grades the work.

The commits are attributed to the operator and signed with a key dedicated to
the Loop, which is what tells a Loop commit from a hand-authored one. A Verified
signature here asserts that the operator caused the commit, not that he wrote
it.

Closes #92

[JacobStephens2]

Run ended: agent-failed (exit 4)

• Task: Installer auto-detects binaries for the invoking user, not the configured service_user #92
• Ended by: agent-failed
• Exit code: 4
• Iterations: 1 (committed 0, no-op 1, killed 0, turn bound 0)
• Faults: agent-failed
• Proposal: Loop: Installer auto-detects binaries for the invoking user, not the configured service_user #109

Nothing is merged, deployed or applied. Read PROGRESS.md on this branch first.