Offer to send the log to us when an install or update fails

When update or install.sh fails and there's a terminal, ask whether to
send its log to the CoreDesktop team, with the option of reading exactly
what would be sent first. Nothing is sent without a yes, and nothing is
asked without a terminal. The new report command sends a log later
(report, report FILE) or shows what would be sent (report --view).

Before sending, the log is cleaned of terminal codes, and the home
folder, user name, host name, email addresses, IPv4 addresses and
Tailscale names are replaced. CoreDesktop's version, the kernel's, the
failed steps and sibling versions go along with it. The request format
the receiver on federated.sh implements is described at the top of
report.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/update.bats

@@ -11,7 +11,7 @@ setup() {
   CD="$HOME/.local/share/coredesktop"
   mkdir -p "$CD/updates.d" "$HOME/.local/bin"
   cp "$REPO/update" "$CD/update"
-  for script in refresh sibling version configure audit; do
+  for script in refresh sibling version configure audit report; do
     echo '#!/bin/bash' > "$CD/$script"
   done
 
@@ -51,7 +51,7 @@ ran() {
   [[ "$output" == *"Done."* ]]
   called git -C "$CD" pull --ff-only
   ran a b
-  for script in update refresh sibling version configure audit; do
+  for script in update refresh sibling version configure audit report; do
     [ -x "$HOME/.local/bin/$script" ]
   done
 }
@@ -188,6 +188,26 @@ ran() {
   [[ "$output" == *"The full output is in $HOME/.local/state/coredesktop/logs/update-"*".log"* ]]
 }
 
+@test "when a step fails, update offers to send its log, naming what failed" {
+  printf '#!/bin/bash\nprintf "%%s\\n" "$@" > "$BATS_TEST_TMPDIR/report-args"\n' > "$CD/report"
+  hook 10-a 'return 1'
+  hook 20-b 'return 1'
+
+  run "$CD/update"
+  [ "$status" -eq 1 ]
+  log=("$HOME"/.local/state/coredesktop/logs/update-*.log)
+  [ "$(cat "$BATS_TEST_TMPDIR/report-args")" = "$(printf '%s\n' --offer "${log[0]}" 10-a.sh 20-b.sh)" ]
+}
+
+@test "update doesn't offer to send its log when nothing failed" {
+  printf '#!/bin/bash\ntouch "$BATS_TEST_TMPDIR/report-ran"\n' > "$CD/report"
+  hook 10-a 'true'
+
+  run "$CD/update"
+  [ "$status" -eq 0 ]
+  [ ! -e "$BATS_TEST_TMPDIR/report-ran" ]
+}
+
 @test "clean_log leaves only the text of a terminal session's log" {
   eval "$(sed -n '/^clean_log() {/,/^}/p' "$REPO/update")"
   log="$BATS_TEST_TMPDIR/session.log"