[Bug]: feature.json branch bypass is inconsistent — check-prerequisites ignores it (bash + PowerShell) #2887

Bug Description

The "must be on a feature branch" check can be bypassed when .specify/feature.json pins an existing feature directory (feature_json_matches_feature_dir / Test-FeatureJsonMatchesFeatureDir). setup-plan and setup-tasks apply this bypass; check-prerequisites does not in its validating modes. So with the same feature.json on the same branch, half the spec-kit commands succeed and half fail.

This affects both the bash and PowerShell script sets.

Evidence (main @ 7106858)

The helper is called from only two of the three scripts, in each language:

scripts/bash/common.sh:191            feature_json_matches_feature_dir()
scripts/bash/setup-plan.sh:36         guarded ✅
scripts/bash/setup-tasks.sh:32        guarded ✅
scripts/bash/check-prerequisites.sh:115   check_feature_branch — UNGUARDED ❌

scripts/powershell/common.ps1:169     Test-FeatureJsonMatchesFeatureDir
scripts/powershell/setup-plan.ps1:27  guarded ✅
scripts/powershell/setup-tasks.ps1:23 guarded ✅
scripts/powershell/check-prerequisites.ps1:85   Test-FeatureBranch — UNGUARDED ❌

--paths-only / -PathsOnly exits before the branch check, which is why only that mode happens to work.

Command → script mapping

Steps to Reproduce

On a branch whose name is not a feature pattern, with feature.json pinning a valid populated feature dir:

bash .specify/scripts/bash/setup-plan.sh --json                  # EXIT=0
bash .specify/scripts/bash/check-prerequisites.sh --json --paths-only  # EXIT=0
bash .specify/scripts/bash/check-prerequisites.sh --json         # EXIT=1  "Not on a feature branch"
bash .specify/scripts/bash/check-prerequisites.sh --json --require-tasks --include-tasks  # EXIT=1

Expected Behavior

check-prerequisites honors feature.json the same way setup-plan / setup-tasks do, so the whole command set behaves consistently. The bypass only skips the branch-name check, not the file-existence checks (plan.md, tasks.md).

Actual Behavior

check-prerequisites fails with "Not on a feature branch" even though feature.json pins a valid feature dir, blocking /speckit.checklist, /speckit.analyze, /speckit.implement, /speckit.taskstoissues.

Specify CLI Version

main @ 7106858 (reported on 0.9.3)

AI Agent

Codex CLI

Suggested Fix

Wrap the branch check in both check-prerequisites.sh and check-prerequisites.ps1 with the same guard the setup scripts use:

if ! feature_json_matches_feature_dir "$REPO_ROOT" "$FEATURE_DIR"; then
    check_feature_branch "$CURRENT_BRANCH" "$HAS_GIT" || exit 1
fi

REPO_ROOT / FEATURE_DIR are already in scope at that point. PR incoming.