fix(office-hours): diff against origin/HEAD, not a hard-coded origin/main with stderr hidden (#3347)

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

office-hours/SKILL.md

@@ -509,7 +509,7 @@ SLUG=$(~/.claude/skills/gstack/bin/gstack-slug --get SLUG 2>/dev/null)
 ```
 
 1. Read `CLAUDE.md`, `TODOS.md` (if they exist).
-2. Run `git log --oneline -30` and `git diff origin/main --stat 2>/dev/null` to understand recent context.
+2. Run `git log --oneline -30` and `git diff origin/HEAD --stat` (default branch) to grasp recent context.
 3. Use Grep/Glob to map the codebase areas most relevant to the user's request.
 4. **List existing design docs for this project:**
    ```bash

office-hours/SKILL.md.tmpl

@@ -81,7 +81,7 @@ Understand the project and the area the user wants to change.
 ```
 
 1. Read `CLAUDE.md`, `TODOS.md` (if they exist).
-2. Run `git log --oneline -30` and `git diff origin/main --stat 2>/dev/null` to understand recent context.
+2. Run `git log --oneline -30` and `git diff origin/HEAD --stat` (default branch) to grasp recent context.
 3. Use Grep/Glob to map the codebase areas most relevant to the user's request.
 4. **List existing design docs for this project:**
    ```bash