feat(bad): auto-detect and chain existing statusLine during setup

Setup now scans settings files highest→lowest precedence, finds the
effective statusLine command, chains it stdin-safely into bad-statusline.sh,
and writes only to settings.local.json — no other files touched.
Detailed logic extracted to references/coordinator/setup-statusline-hook.md.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

skills/bad/assets/module-setup.md

@@ -51,30 +51,7 @@ Ask: **"Install BAD session-state capture (writes rate-limit / context data to a
 
 Default: **yes** (or auto-accept if `--headless` / `accept all defaults`).
 
-If **yes**:
-
-1. Copy `./assets/bad-statusline.sh` to `{project-root}/.claude/bad-statusline.sh`.
-   Make it executable: `chmod +x {project-root}/.claude/bad-statusline.sh`.
-
-2. Read `{project-root}/.claude/settings.json` (create `{}` if absent).
-
-3. Check if a `statusLine` key already exists:
-   - **If absent:** set it to:
-     ```json
-     "statusLine": {
-       "type": "command",
-       "command": ".claude/bad-statusline.sh"
-     }
-     ```
-   - **If already set:** do not overwrite. Instead, print:
-     ```
-     ⚠️  A statusLine is already configured in .claude/settings.json.
-     To enable BAD's session-state capture, chain it manually:
-       1. Open .claude/bad-statusline.sh — it shows how to pipe to an existing script.
-       2. Add .claude/bad-statusline.sh as the last step in your existing statusline pipeline.
-     ```
-
-4. Write the updated `settings.json` back (only if you modified it).
+If **yes**, read and follow `references/coordinator/setup-statusline-hook.md`.
 
 ---
 

skills/bad/references/coordinator/setup-statusline-hook.md

@@ -0,0 +1,74 @@
+# BAD Session-State Hook Setup
+
+Executed during `/bad setup` (Step 2b). Installs `bad-statusline.sh` as the Claude Code
+`statusLine` script, automatically chaining any pre-existing statusLine command so the user
+loses no existing functionality.
+
+---
+
+## Step 1: Find the Effective Existing Command
+
+Claude Code applies `statusLine` using this precedence (highest to lowest). Scan in order and
+stop at the first file that has a `statusLine.command`. Skip any command already equal to
+`.claude/bad-statusline.sh` (re-run guard).
+
+| Priority | File | Writable by setup |
+|----------|------|-------------------|
+| 1 (highest) | `/Library/Application Support/ClaudeCode/managed-settings.json` | No |
+| 2 | `{project-root}/.claude/settings.local.json` | Yes |
+| 3 | `{project-root}/.claude/settings.json` | No — local.json takes precedence |
+| 4 (lowest) | `~/.claude/settings.json` | No — outside project scope |
+
+- If found at priority 1 (managed): set `MANAGED_CONFLICT=true` — go directly to the managed
+  warning below and stop. Writing to `settings.local.json` would have no effect since managed
+  settings override all user-writable files.
+- If found at priority 2–4: save the value as `CHAIN_COMMAND`.
+- If not found anywhere: `CHAIN_COMMAND` is empty.
+
+---
+
+## Step 2: Write `bad-statusline.sh`
+
+Copy `./assets/bad-statusline.sh` to `{project-root}/.claude/bad-statusline.sh`.
+Make it executable: `chmod +x {project-root}/.claude/bad-statusline.sh`.
+
+If `CHAIN_COMMAND` is non-empty, rewrite the script body:
+
+```bash
+#!/bin/bash
+# BAD session-state capture — auto-generated by /bad setup.
+# Chains pre-existing statusLine command then writes Claude Code session JSON
+# to a temp file for BAD Pre-Continuation Checks.
+SESSION_JSON=$(cat)
+echo "$SESSION_JSON" | <CHAIN_COMMAND>
+echo "$SESSION_JSON" > "${TMPDIR:-/tmp}/bad-session-state.json"
+```
+
+If `CHAIN_COMMAND` is empty, keep the script body as-is.
+
+---
+
+## Step 3: Write `statusLine` to Project-Local Settings
+
+Read `{project-root}/.claude/settings.local.json` (create `{}` if absent). Set:
+
+```json
+"statusLine": {
+  "type": "command",
+  "command": ".claude/bad-statusline.sh"
+}
+```
+
+Write the file back. No other settings files are modified.
+
+---
+
+## Managed Settings Conflict
+
+If `MANAGED_CONFLICT=true`, skip Steps 2–3 and print:
+
+```
+⚠️  A managed statusLine is configured and takes precedence over all user settings.
+    BAD session-state capture (rate-limit pausing, context compaction) will not function.
+    Ask your admin to chain .claude/bad-statusline.sh into the managed statusLine script.
+```