Fix OpenWrt procd smoke: anchor sentinel matching and escape [owrt] in expect puts

[Copilot]

The OpenWrt procd smoke expect driver matched bare "FETCH_OK" / "FETCH_FAIL" / "NETUP_DONE" substrings, so the serial console's echo of the sent command line (... && echo FETCH_OK || echo FETCH_FAIL) satisfied the success branch before the guest printed the real result — a failed uclient-fetch went unnoticed and the script continued to the missing /tmp/guest-smoke.sh. The eventual timeout branch then died with invalid command name "owrt" because unescaped [owrt] in puts triggers Tcl command substitution, masking the true failure point (CI runs 27677458092, 27816136090).

Changes (test/openwrt/run.sh)

• Anchor sentinel matching to standalone output lines: "FETCH_OK", "FETCH_FAIL", and "NETUP_DONE" glob matches replaced with -re {[\r\n]MARKER[\r\n]}. In the echoed command line the markers are preceded by a space, so only the real guest output (\r\n-delimited) matches — the fetch-failure branch now fires immediately with exit 3.
• Escape [owrt] literals in Tcl puts: all 5 occurrences changed to \[owrt\] so timeout/error messages print correctly instead of raising a Tcl error.

expect {
	-re {[\r\n]FETCH_OK[\r\n]}   {}
	-re {[\r\n]FETCH_FAIL[\r\n]} { puts "\n\[owrt\] cannot reach host HTTP server"; exit 3 }
	timeout      { puts "\n\[owrt\] fetch timeout"; exit 3 }
}

Verified against simulated serial output (command echo followed by FETCH_FAIL, plus the RTNETLINK answers: Network unreachable noise before NETUP_DONE seen in the failing runs): the fail path now exits through the fetch-failure branch, and the success path still matches the standalone marker lines.