fix: v0.9.1 robustness cleanups

- run_resume falls back to a new conversation only when the transcript file
  is gone; other failures end at the menu with the recorded id intact.
- The SessionStart hook resolves the session name under the registry lock;
  rename holds it across tmux rename-session and the registry move
  (dd_registry_locked, nestable).
- dd_load_env parses KEY=value like systemd instead of sourcing the files.
- devdesk-deploy: DPkg::Lock::Timeout, explicit FAILED lines on stdout and in
  the log; the hook answers synchronously and CI checks the HTTP status.
  logrotate for the deploy log.
- postinst drops duplicate terminal-features entries; hooks sweep stale
  temp files.

Closes #12

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

libexec/devdesk-deploy

@@ -3,6 +3,9 @@
 # listener (hook "devdesk-deploy") when CI publishes a v* tag; the tag's ref is
 # passed as $1. Safe for running sessions: package upgrades restart only
 # devdesk.service (ttyd), never devdesk-tmux.service where Claude lives.
+#
+# The hook runs this synchronously and returns its output, with HTTP 500 when
+# it fails, so CI's "Deploy to CT 126" job shows the real result (devdesk#12).
 set -euo pipefail
 
 LOG=${DEVDESK_DEPLOY_LOG:-/var/log/devdesk-deploy.log}
@@ -12,11 +15,28 @@ log() {
     printf '%s %s\n' "$(date '+%F %T')" "$*" >>"$LOG"
 }
 
-exec 9>/run/devdesk-deploy.lock
-flock -w 900 9 || {
-    log "another deploy is still running; giving up"
+# The outcome goes to the log and to stdout (the webhook response).
+say() {
+    log "$*"
+    printf '%s\n' "$*"
+}
+fail() {
+    say "deploy FAILED: $*"
     exit 1
 }
+on_error() {
+    local rc=$?
+    say "deploy FAILED: line $1 exited $rc (details in $LOG)"
+    exit "$rc"
+}
+trap 'on_error $LINENO' ERR
+
+# Wait for dpkg/apt rather than fail when unattended-upgrades or a manual apt
+# run holds the lock.
+APT_OPTS=(-o DPkg::Lock::Timeout=120 -o Dpkg::Use-Pty=0)
+
+exec 9>/run/devdesk-deploy.lock
+flock -w 900 9 || fail "another deploy is still running"
 
 want=${1:-}
 want=${want#refs/tags/}
@@ -25,7 +45,7 @@ before=$(dpkg-query -W -f='${Version}' devdesk 2>/dev/null || echo none)
 log "=== deploy: installed $before, release ${want:-latest}"
 
 refresh() {
-    apt-get update -q -o Dir::Etc::sourcelist="$SOURCES" -o Dir::Etc::sourceparts=- \
+    apt-get update -q "${APT_OPTS[@]}" -o Dir::Etc::sourcelist="$SOURCES" -o Dir::Etc::sourceparts=- \
         -o APT::Get::List-Cleanup=0 >>"$LOG" 2>&1
 }
 
@@ -41,14 +61,17 @@ for _ in $(seq 1 18); do
 done
 
 if [ -n "$want" ] && [ "$candidate" != "$want" ]; then
-    log "registry still offers $candidate, not $want; giving up"
-    exit 1
+    fail "the registry still offers ${candidate:-nothing}, not $want"
 fi
 if [ "$candidate" = "$before" ]; then
-    log "already at $before; nothing to do"
+    say "already at $before; nothing to do"
     exit 0
 fi
 
-DEBIAN_FRONTEND=noninteractive apt-get install -y -q --only-upgrade \
+DEBIAN_FRONTEND=noninteractive apt-get install -y -q --only-upgrade "${APT_OPTS[@]}" \
     -o Dpkg::Options::=--force-confold devdesk </dev/null >>"$LOG" 2>&1
-log "devdesk $before -> $(dpkg-query -W -f='${Version}' devdesk)"
+after=$(dpkg-query -W -f='${Version}' devdesk)
+if [ -n "$want" ] && [ "$after" != "$want" ]; then
+    fail "installed $after, not $want"
+fi
+say "devdesk $before -> $after"