fix(guardrails): treat the heredoc body of git commit -F - and git tag -F - as data in block-root-delete-target #7379

Refs: #6625

Outcome

The one-line form git commit -F - <<'EOF' and git tag -F - <<'EOF' (every argument on the opener's line), whose message mentions a root delete target, is no longer refused by block-root-delete-target. Every other heredoc reader keeps being scanned.

Current behavior

plugins/guardrails/hooks/block-root-delete-target.sh rdt_hd_reader (about lines 3037-3053) treats a quoted-delimiter heredoc body as data only when the command is cat or gh pr|issue|api|release. A commit message written in the one-line form git commit -F - <<'EOF' gets scanned, so a message that names a delete target is refused.

Desired behavior

rdt_hd_reader also returns true when, and only when, the words are exactly: word 0 git, word 1 commit or tag, and the arguments include -F -. Any git global option before the subcommand (-c, -C, --exec-path, --git-dir and the like) does not match. Neither does any other git subcommand, bash <<'EOF', a pipe, or cat > file. The comment above the function is updated: it keeps the !sh reason for every other git word, and says commit and tag are exempt because git ignores an alias that hides a built-in command (git-config(1), alias.*).

Scope fence

• plugins/guardrails/hooks/block-root-delete-target.sh (the rdt_hd_reader function and its comment only)
• plugins/guardrails/hooks/block-root-delete-target.test.sh
• .changes/guardrails/<slug>.md

Acceptance criteria

• New stay-quiet cases: git commit -F - <<'EOF' and git tag -F - <<'EOF', each with a body that names a root delete target, exit 0.
• New block cases: git -c alias.x=y commit -F - <<'EOF', git -C /tmp commit -F - <<'EOF' and an unknown git alias with the same body still block. So do the existing bash <<'EOF' cases, and a git commit -F - --trailer "<x>" \ form whose <<'EOF' opener sits on a later line.
• The PR body asks the human merger to confirm that the stay-quiet cases fail on the base commit, as the hook-precision rule requires.
• The PR's CI runs plugins/guardrails/hooks/block-root-delete-target.test.sh and it passes.
• A guardrails changelog fragment exists and scripts/check-changelog-fragments.sh --check passes.
• The PR body carries Hold: a human merges this.

Out of scope

• Any other reader (tee, bash, other git subcommands, interpreters).
• --file=- and --file -: fix(guardrails): block-root-delete-target judges backticks inside a quoted heredoc body #6625's decision admits only -F -.
• The multi-line or trailer form stays scanned; do not relax rdt_hd_plain.
• Other guards.