chore: require gstack for AI-assisted work (#10)

Add gstack team mode (required) bootstrap: a CLAUDE.md section that checks
for a global gstack install, a PreToolUse hook on the Skill tool that blocks
skill use when gstack is missing, and the project settings registering it.

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

Author: effinrich

.claude/hooks/check-gstack.sh

@@ -0,0 +1,29 @@
+#!/bin/bash
+# Block skill usage when gstack is not installed globally.
+#
+# Resolve the install root the way gstack skill preambles do: the GSTACK_ROOT
+# env var first, then every host's global install location, then the migrated
+# repo location. Block only when NONE exist (#2500 — hardcoding
+# ~/.claude/skills/gstack false-blocked Codex-host and migrated-repo installs).
+_GSTACK_ROOT=""
+for _D in "${GSTACK_ROOT:-}" "$HOME/.claude/skills/gstack" "$HOME/.codex/skills/gstack" "$HOME/.factory/skills/gstack" "$HOME/.kiro/skills/gstack" "$HOME/.config/opencode/skills/gstack" "$HOME/.slate/skills/gstack" "$HOME/.cursor/skills/gstack" "$HOME/.openclaw/skills/gstack" "$HOME/.hermes/skills/gstack" "$HOME/.gbrain/skills/gstack" "$HOME/.gstack/repos/gstack"; do
+  [ -z "$_GSTACK_ROOT" ] && [ -n "$_D" ] && [ -d "$_D/bin" ] && _GSTACK_ROOT="$_D"
+done
+
+if [ -z "$_GSTACK_ROOT" ]; then
+  cat >&2 <<'MSG'
+BLOCKED: gstack is not installed globally.
+
+gstack is required for AI-assisted work in this repo.
+
+Install it:
+  git clone --depth 1 https://github.com/garrytan/gstack.git ~/.claude/skills/gstack
+  cd ~/.claude/skills/gstack && ./setup --team
+
+Then restart your AI coding tool.
+MSG
+  echo '{"hookSpecificOutput":{"hookEventName":"PreToolUse","permissionDecision":"deny","permissionDecisionReason":"gstack is required but not installed. See stderr for install instructions."}}'
+  exit 2
+fi
+
+echo '{}'

.claude/settings.json

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+{
+  "hooks": {
+    "PreToolUse": [
+      {
+        "matcher": "Skill",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "\"$CLAUDE_PROJECT_DIR/.claude/hooks/check-gstack.sh\""
+          }
+        ]
+      }
+    ]
+  }
+}

CLAUDE.md

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+## gstack (REQUIRED — global install)
+
+**Before doing ANY work, verify gstack is installed:**
+
+```bash
+_GS=""
+for _D in "${GSTACK_ROOT:-}" "$HOME/.claude/skills/gstack" "$HOME/.codex/skills/gstack" "$HOME/.factory/skills/gstack" "$HOME/.kiro/skills/gstack" "$HOME/.config/opencode/skills/gstack" "$HOME/.slate/skills/gstack" "$HOME/.cursor/skills/gstack" "$HOME/.openclaw/skills/gstack" "$HOME/.hermes/skills/gstack" "$HOME/.gbrain/skills/gstack" "$HOME/.gstack/repos/gstack"; do
+  [ -z "$_GS" ] && [ -n "$_D" ] && [ -d "$_D/bin" ] && _GS="$_D"
+done
+[ -n "$_GS" ] && echo "GSTACK_OK: $_GS" || echo "GSTACK_MISSING"
+```
+
+If GSTACK_MISSING: STOP. Do not proceed. Tell the user:
+
+> gstack is required for all AI-assisted work in this repo.
+> Install it:
+>
+> ```bash
+> git clone --depth 1 https://github.com/garrytan/gstack.git ~/.claude/skills/gstack
+> cd ~/.claude/skills/gstack && ./setup --team
+> ```
+>
+> Then restart your AI coding tool.
+
+Do not skip skills, ignore gstack errors, or work around missing gstack.
+
+Using gstack skills: After install, skills like /qa, /ship, /review, /investigate,
+and /browse are available. Use /browse for all web browsing (Aside first, the bundled gstack browser as fallback).
+Use the resolved install path above for gstack file paths
+(default: ~/.claude/skills/gstack).