Host-scoped update-restart obligation (061195fac1 / 953b6f6f08 / 3be255eca6)
lands on the PM model: the obligation record, its readers and the legacy
per-home marker compat come in as-is. The catch-up restart path
(`_apply_pending_fleet_restart_catchup` / `_run_pending_fleet_restart`) is
retired here (the fleet restart rides the completion owner), so main's
per-host restart-once guard on that path is not carried; its unit→live
MainPID collapse IS ported into the live post-update systemd pass
(`_restart_systemd_gateway_units`), with the two collapse tests rewritten
against that function (red on the pre-port tree: `_unit_main_pid` absent).
Tests that exercised only the retired catch-up path are dropped.
Desktop: main's shared log-rotation planner replaces the inline constants
in main.ts; the merge keeps our machine-profile import beside its import.
utf-8 → utf-8-sig on the three new BOM-intolerant reads (footguns lint).
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