Phase D: cross-runtime tweaks (visual-companion, executing-plans, test)

Misc platform/runtime statements and adjacencies that don't fit the
prose, config-ref, README-ordering, or tool-vocabulary buckets:

- visual-companion frame template: rename CSS/HTML id #claude-content
  → #frame-content. The id is purely styling — nothing external
  references it. The brainstorm-server test that asserted the old
  string is updated in lockstep.

- visual-companion launch instructions: add a Copilot CLI section
  alongside Claude Code, Codex, and Gemini CLI; combine the Claude
  Code (macOS / Linux) and (Windows) sections so heading style
  matches the other (non-OS-qualified) platforms.

- visual-companion: "Use Write tool" → "Use your file-creation tool"
  for the cat/heredoc warning. The prohibition is what's load-
  bearing, not the tool name.

- executing-plans/SKILL.md: list all subagent-capable runtimes
  (Claude Code, Codex CLI, Codex App, Copilot CLI, Gemini CLI) and
  point at the per-platform tool refs as the source of truth.

- executing-plans/SKILL.md: relative path "using-superpowers/
  references/" → "../using-superpowers/references/" to resolve
  correctly from the executing-plans/ directory.

No bundled spec doc here — Phase D was scope-extension work that
took place across rounds, with no standalone spec authored.

skills/brainstorming/visual-companion.md

@@ -49,20 +49,13 @@ Save `screen_dir` and `state_dir` from the response. Tell user to open the URL.
 
 **Launching the server by platform:**
 
-**Claude Code (macOS / Linux):**
+**Claude Code:**
 ```bash
-# Default mode works — the script backgrounds the server itself
+# Default mode works — the script backgrounds the server itself.
 scripts/start-server.sh --project-dir /path/to/project
 ```
 
-**Claude Code (Windows):**
-```bash
-# Windows auto-detects and uses foreground mode, which blocks the tool call.
-# Use run_in_background: true on the Bash tool call so the server survives
-# across conversation turns.
-scripts/start-server.sh --project-dir /path/to/project
-```
-When calling this via the Bash tool, set `run_in_background: true`. Then read `$STATE_DIR/server-info` on the next turn to get the URL and port.
+On Windows, the script auto-detects and switches to foreground mode (which blocks the tool call). Use `run_in_background: true` on the Bash tool call so the server survives across conversation turns, then read `$STATE_DIR/server-info` on the next turn to get the URL and port.
 
 **Codex:**
 ```bash
@@ -78,6 +71,14 @@ scripts/start-server.sh --project-dir /path/to/project
 scripts/start-server.sh --project-dir /path/to/project --foreground
 ```
 
+**Copilot CLI:**
+```bash
+# Use --foreground and start the server via the bash tool with mode: "async"
+# so the process survives across turns. Capture the returned shellId for
+# read_bash / stop_bash if you need to interact with it later.
+scripts/start-server.sh --project-dir /path/to/project --foreground
+```
+
 **Other environments:** The server must keep running in the background across conversation turns. If your environment reaps detached processes, use `--foreground` and launch the command with your platform's background execution mechanism.
 
 If the URL is unreachable from your browser (common in remote/containerized setups), bind a non-loopback host:
@@ -97,7 +98,7 @@ Use `--url-host` to control what hostname is printed in the returned URL JSON.
    - Before each write, check that `$STATE_DIR/server-info` exists. If it doesn't (or `$STATE_DIR/server-stopped` exists), the server has shut down — restart it with `start-server.sh` before continuing. The server auto-exits after 30 minutes of inactivity.
    - Use semantic filenames: `platform.html`, `visual-style.html`, `layout.html`
    - **Never reuse filenames** — each screen gets a fresh file
-   - Use Write tool — **never use cat/heredoc** (dumps noise into terminal)
+   - Use your file-creation tool — **never use cat/heredoc** (dumps noise into terminal)
    - Server automatically serves the newest file
 
 2. **Tell user what to expect and end your turn:**