fix: shellcheck TODO has no enforcement — || true may never be removed (#71)

- Fix SC2164: add || exit 1 to bare cd in update-prompt.sh
- Fix SC2155: separate declare and assign in env.sh, supervisor-poll.sh, dev-agent.sh
- Fix SC2034: inline suppression for vars used by sourced helpers
- Remove unused `mergeable` declaration, rename unused loop var to `_w`
- Remove || true from shellcheck CI step — failures are now blocking

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/env.sh

@@ -82,7 +82,8 @@ matrix_send() {
   [ -z "${MATRIX_TOKEN:-}" ] && return 0
   local prefix="$1" msg="$2" thread_id="${3:-}" ctx_tag="${4:-}"
   local room_encoded="${MATRIX_ROOM_ID//!/%21}"
-  local txn="$(date +%s%N)$$"
+  local txn
+  txn="$(date +%s%N)$$"
   local body
   if [ -n "$thread_id" ]; then
     body=$(jq -nc --arg m "[${prefix}] ${msg}" --arg t "$thread_id" \

lib/matrix_listener.sh

@@ -34,6 +34,7 @@ if [ -z "${MATRIX_TOKEN:-}" ] || [ -z "${MATRIX_ROOM_ID:-}" ]; then
 fi
 
 # URL-encode room ID
+# shellcheck disable=SC2034
 ROOM_ENCODED="${MATRIX_ROOM_ID//!/%21}"
 
 # Build sync filter — only our room, only messages
@@ -108,6 +109,7 @@ while true; do
   while IFS= read -r event; do
     SENDER=$(printf '%s' "$event" | jq -r '.sender')
     BODY=$(printf '%s' "$event" | jq -r '.content.body // ""')
+    # shellcheck disable=SC2034
     EVENT_ID=$(printf '%s' "$event" | jq -r '.event_id')
 
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