[Bug]: check-prerequisites.sh --paths-only still runs branch validation, contradicting --help

## Bug Description

`scripts/bash/check-prerequisites.sh --paths-only` is documented as "no validation" / "no prerequisite validation", but the script runs `check_feature_branch` **before** the `--paths-only` early exit. The result: when the current branch does not match the feature-branch naming convention, `--paths-only` exits non-zero with a branch-format error, even though the caller asked for paths only and explicitly opted out of validation.

Source: https://github.com/github/spec-kit/blob/main/scripts/bash/check-prerequisites.sh#L81-L113

```bash
# Get feature paths and validate branch
_paths_output=$(get_feature_paths) || { ... ; exit 1; }
eval "$_paths_output"
unset _paths_output
check_feature_branch "$CURRENT_BRANCH" "$HAS_GIT" || exit 1 # ← runs even with --paths-only

# If paths-only mode, output paths and exit (support JSON + paths-only combined)
if \$PATHS_ONLY; then
...
exit 0
fi
```

The header documentation (line 14) says: \`--paths-only Only output path variables (no validation)\` and \`--help\` (line 54) says \`(no prerequisite validation)\`. Branch validation is the most user-visible form of validation, so this contradicts the documented behavior.

## Steps to Reproduce

1. Initialize a Spec Kit project: \`specify init test-paths-only --integration claude\`
2. Switch to a non-feature branch: \`git checkout -b chore/some-cleanup\`
3. Run paths-only: \`./.specify/scripts/bash/check-prerequisites.sh --paths-only\`

## Expected Behavior

\`--paths-only\` succeeds and emits \`REPO_ROOT\`, \`BRANCH\`, \`FEATURE_DIR\`, etc., regardless of branch name (the caller asked for paths, not validation).

## Actual Behavior

Exit 1 with branch-validation error (the message produced by \`check_feature_branch\` in \`common.sh\`), no path variables emitted.

## Specify CLI Version

0.7.4.dev0

## AI Agent

Claude Code

## Suggested Fix

Move \`check_feature_branch\` after the \`if \$PATHS_ONLY; then ... exit 0; fi\` block so \`--paths-only\` truly skips validation. Same source ordering already exists in \`scripts/powershell/check-prerequisites.ps1\` — please verify both are aligned.

## Context

Surfaced while bulk-installing Spec Kit across 20 internal projects. \`/speckit-tasks\` and similar commands invoke \`check-prerequisites.sh --paths-only --json\` from non-feature chore branches and unexpectedly fail with branch-format errors despite the documented opt-out.