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.

README.md

@@ -20,7 +20,6 @@ Superpowers is a complete software development methodology for your coding agent
   - [Kimi Code](#kimi-code)
   - [OpenCode](#opencode)
   - [Pi](#pi)
-  - [Qwen Code](#qwen-code)
   - [Hermes Agent](#hermes-agent)
 - [The Basic Workflow](#the-basic-workflow)
 - [Community](#community)
@@ -247,22 +246,6 @@ pi -e /path/to/superpowers
 
 The Pi package loads the Superpowers skills and a small extension that injects the `using-superpowers` bootstrap at session startup and again after compaction. Pi has native skills, so no compatibility `Skill` tool is required. Subagent and task-list tools remain optional Pi companion packages.
 
-### Qwen Code
-
-Qwen Code installs plugins from Claude Code marketplaces directly.
-
-- Install the plugin from this repository, and pick `superpowers` when prompted:
-
-  ```bash
-  qwen extensions install obra/superpowers
-  ```
-
-- Update later:
-
-  ```bash
-  qwen extensions update superpowers
-  ```
-
 ### Hermes Agent
 
 Install Superpowers as a Hermes plugin from this repository:

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)
 ```