fix(requesting-code-review): anchor the multi-commit BASE_SHA alternative to the merge base

The '# or origin/main' alternative fed a moving ref into the reviewer's
two-dot diff: once origin/main advances past the branch point, main's new
files appear as phantom deletions the reviewer can't distinguish from real
ones. Reproduced during triage (2026-08-12): a scratch repo with main
advanced one commit shows 'main-new.txt | 1 -' in the branch's diff.
git merge-base origin/main HEAD anchors the range to the branch point,
matching how sdd's review-package already computes BASE.

Reported in #2118 (wan-huiyan). Fixes #2118.

skills/requesting-code-review/SKILL.md

@@ -25,7 +25,7 @@ Dispatch a code reviewer subagent to catch issues before they cascade. The revie
 
 **1. Get git SHAs:**
 ```bash
-BASE_SHA=$(git rev-parse HEAD~1)  # or origin/main
+BASE_SHA=$(git rev-parse HEAD~1)  # or: git merge-base origin/main HEAD
 HEAD_SHA=$(git rev-parse HEAD)
 ```
 

skills/subagent-driven-development/scripts/review-package

@@ -25,9 +25,7 @@ git rev-parse --verify --quiet "$head" >/dev/null || { echo "bad HEAD: $head" >&
 if [ $# -eq 4 ]; then
   out=$4
 else
-  # Invoke via bash rather than direct exec: some extractors (Python zipfile)
-  # strip Unix exec bits when unpacking marketplace packages (#2040).
-  dir=$("${BASH:-bash}" "$(cd "$(dirname "$0")" && pwd)/sdd-workspace" "$plan")
+  dir=$("$(cd "$(dirname "$0")" && pwd)/sdd-workspace" "$plan")
   out="$dir/review-$(git rev-parse --short "$base")..$(git rev-parse --short "$head").diff"
 fi
 

skills/subagent-driven-development/scripts/task-brief

@@ -21,9 +21,7 @@ n=$2
 if [ $# -eq 3 ]; then
   out=$3
 else
-  # Invoke via bash rather than direct exec: some extractors (Python zipfile)
-  # strip Unix exec bits when unpacking marketplace packages (#2040).
-  dir=$("${BASH:-bash}" "$(cd "$(dirname "$0")" && pwd)/sdd-workspace" "$plan")
+  dir=$("$(cd "$(dirname "$0")" && pwd)/sdd-workspace" "$plan")
   out="$dir/task-${n}-brief.md"
 fi
 

tests/claude-code/test-sdd-workspace.sh

@@ -189,21 +189,6 @@ PLAN
         echo "    status: $wt_status"
     fi
 
-    # --- helpers survive a mode-stripping extractor dropping exec bits (#2040) ---
-    local stripped="$TEST_ROOT/stripped-scripts"
-    mkdir -p "$stripped"
-    cp "$SDD_SCRIPTS/sdd-workspace" "$SDD_SCRIPTS/task-brief" "$SDD_SCRIPTS/review-package" "$stripped/"
-    chmod -x "$stripped"/*
-    local noexec_out noexec_rc=0
-    noexec_out="$(cd "$repo" && bash "$stripped/task-brief" plan-b.md 1 2>&1)" || noexec_rc=$?
-    if [[ "$noexec_rc" -eq 0 && -f "$repo/.superpowers/sdd/plan-b/task-1-brief.md" ]]; then
-        pass "task-brief works with no exec bit on sdd-workspace"
-    else
-        fail "task-brief works with no exec bit on sdd-workspace"
-        echo "    rc: $noexec_rc"
-        echo "    output: $noexec_out"
-    fi
-
     echo ""
     if [[ "$FAILURES" -ne 0 ]]; then
         echo "FAILED: $FAILURES assertion(s)."