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>

review/review-poll.sh

@@ -12,7 +12,9 @@ export PROJECT_TOML="${1:-}"
 source "$(dirname "$0")/../lib/env.sh"
 
 
+# shellcheck disable=SC2034
 REPO="${CODEBERG_REPO}"
+# shellcheck disable=SC2034
 REPO_ROOT="${PROJECT_REPO_ROOT}"
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
 

review/review-pr.sh

@@ -29,7 +29,9 @@ git -C "$FACTORY_ROOT" pull --ff-only origin main 2>/dev/null || true
 
 PR_NUMBER="${1:?Usage: review-pr.sh <pr-number> [--force]}"
 FORCE="${2:-}"
+# shellcheck disable=SC2034
 REPO="${CODEBERG_REPO}"
+# shellcheck disable=SC2034
 REPO_ROOT="${PROJECT_REPO_ROOT}"
 
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