agent (unreleased): fixes after an independent review — one lock for the writers of agent.json, the trust run serialised and bounded, the CA copy keeps its previous root, the profile stanza from the wrapper's answer, a stale give-up ends, both boot tokens from one read

Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

internal/localapi/guest_boot_key_test.go

@@ -76,6 +76,13 @@ func TestGuestBootKey_AClockStepDoesNotMoveIt(t *testing.T) {
 			t.Errorf("the old token must still be sent when the boot_id is unreadable")
 		}
 	}
+	// what /disks sends: both tokens from ONE read of the guest's init — the init is asked for once, not twice
+	bootID, start = "5b1f6c1e-8f0a-4c56-9d1c-0a8c3b7d2e11", "4242"
+	reads := 0
+	procStarttimeFn = func(string) string { reads++; return start }
+	if id, key := b.GuestBootTokens(ctx, 9201); id != "1794112550-4242" || key != "5b1f6c1e-8f0a-4c56-9d1c-0a8c3b7d2e11-4242" || reads != 1 {
+		t.Errorf("GuestBootTokens = %q, %q after %d read(s) of the init — want both tokens from ONE read", id, key, reads)
+	}
 	bootID, start = "5b1f6c1e-8f0a-4c56-9d1c-0a8c3b7d2e11", "" // the guest does not run
 	if k := b.GuestBootKey(ctx, 9201); k != "" {
 		t.Errorf("a guest that does not run gave the key %q", k)