feat: add Codex CLI as a first-class fourth platform

Rebuilt from scratch following Codex CLI's actual architecture (as
outlined in the review on PR #26). Closes the integration gap with a
proper build adapter, correct install paths, TOML agent files, and
all the architectural differences documented and tested.

What changed vs the previous attempt (PR #26):

- Agents: build adapter generates .toml files (name/description/
  developer_instructions) into dist/codex-cli/.codex/agents/ instead
  of copying .md files with sed transforms
- Skills: installed to .agents/skills/ (correct Codex discovery path)
  instead of .codex/skills/
- Dispatcher: AGENTS.md uses a root-context orchestration header that
  works within agents.max_depth=1 constraints; named-agent routing
  replaced with embedded-instructions workaround for the known
  spawn_agents limitation (openai/codex#15250)
- Tool compat: AskUserQuestion and request_user_input removed; all
  prompts adapted to Codex's actual tool set and approval/confirmation
  flow
- Installer/updater: launchme.sh --platform codex-cli and updateme.sh
  with Codex auto-detection, creating the correct split layout
  (AGENTS.md + .codex/agents/ + .codex/config.toml + .agents/skills/)
- Tests: new per-adapter test suite (tests/adapters/codex-cli/),
  install/update smoke (tests/scripts/codex-cli-install.test.sh), and
  a four-platform parity gate that proves Codex changes do not regress
  Claude Code, Gemini CLI, or OpenCode
- Docs: new codex-cli.md guide, codex-migration.md for users switching
  from other platforms, and README/getting-started/examples updated for
  four-platform positioning
- Bash harness: .gitattributes added to enforce LF on .sh files;
  harness LF-normalized so tests/run.sh works on Windows checkouts
- .gitignore: .planning/ added (internal GSD workflow artifacts)

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

tests/scripts/codex-cli-install.test.sh

@@ -0,0 +1,79 @@
+#!/usr/bin/env bash
+# Tests for Codex CLI install/update flows in scripts/launchme.sh and scripts/updateme.sh
+ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
+
+test_codex_cli_scripts_define_explicit_platform_cases() {
+  local result=0
+  grep -q 'codex-cli)' "$ROOT/scripts/launchme.sh" \
+    || { echo 'launchme.sh should define a codex-cli) case'; result=1; }
+  grep -q 'codex-cli)' "$ROOT/scripts/updateme.sh" \
+    || { echo 'updateme.sh should define a codex-cli) case'; result=1; }
+  grep -q '\.codex/agents' "$ROOT/scripts/updateme.sh" \
+    || { echo 'updateme.sh should detect .codex/agents installs'; result=1; }
+  return $result
+}
+
+test_launchme_installs_codex_cli_layout() {
+  local vault; vault="$(mktemp -d)"
+  local log; log="$(mktemp)"
+
+  if ! bash "$ROOT/scripts/launchme.sh" --platform codex-cli --target "$vault" >"$log" 2>&1; then
+    cat "$log"
+    rm -rf "$vault" "$log"
+    return 1
+  fi
+
+  local result=0
+  [[ -f "$vault/AGENTS.md" ]] || { echo 'AGENTS.md missing after codex-cli install'; result=1; }
+  [[ -f "$vault/.codex/config.toml" ]] || { echo '.codex/config.toml missing after codex-cli install'; result=1; }
+  [[ -d "$vault/.codex/agents" ]] || { echo '.codex/agents missing after codex-cli install'; result=1; }
+  [[ -f "$vault/.codex/agents/transcriber.toml" || -f "$vault/.codex/agents/architect.toml" ]] \
+    || { echo 'core codex agent TOML missing after install'; result=1; }
+  [[ -f "$vault/.agents/skills/onboarding/SKILL.md" ]] || { echo '.agents/skills/onboarding/SKILL.md missing after install'; result=1; }
+
+  if [[ -f "$vault/AGENTS.md" ]]; then
+    grep -q 'Codex CLI' "$vault/AGENTS.md" \
+      || { echo 'AGENTS.md should contain Codex CLI guidance'; result=1; }
+  fi
+  if [[ -f "$vault/.codex/config.toml" ]]; then
+    grep -q '\[agents\]' "$vault/.codex/config.toml" \
+      || { echo '.codex/config.toml should contain [agents]'; result=1; }
+  fi
+
+  rm -rf "$vault" "$log"
+  return $result
+}
+
+test_updateme_auto_detects_and_refreshes_codex_cli_install() {
+  local vault; vault="$(mktemp -d)"
+  local install_log; install_log="$(mktemp)"
+  local update_log; update_log="$(mktemp)"
+
+  if ! bash "$ROOT/scripts/launchme.sh" --platform codex-cli --target "$vault" >"$install_log" 2>&1; then
+    cat "$install_log"
+    rm -rf "$vault" "$install_log" "$update_log"
+    return 1
+  fi
+
+  printf 'stale dispatcher\n' > "$vault/AGENTS.md"
+  printf 'stale config\n' > "$vault/.codex/config.toml"
+
+  if ! printf 'c\n' | bash "$ROOT/scripts/updateme.sh" --target "$vault" >"$update_log" 2>&1; then
+    cat "$update_log"
+    rm -rf "$vault" "$install_log" "$update_log"
+    return 1
+  fi
+
+  local result=0
+  grep -q 'Detected platform: codex-cli' "$update_log" \
+    || { echo 'updateme.sh should auto-detect codex-cli'; result=1; }
+  grep -q 'Codex CLI' "$vault/AGENTS.md" \
+    || { echo 'update should refresh AGENTS.md content'; result=1; }
+  grep -q '\[agents\]' "$vault/.codex/config.toml" \
+    || { echo 'update should refresh .codex/config.toml content'; result=1; }
+  [[ -d "$vault/.codex/agents" ]] || { echo '.codex/agents should remain after update'; result=1; }
+  [[ -d "$vault/.agents/skills" ]] || { echo '.agents/skills should remain after update'; result=1; }
+
+  rm -rf "$vault" "$install_log" "$update_log"
+  return $result
+}