add: Grok transfer lesson — same weatherwise program on a second model

.env.example

@@ -1,8 +1,12 @@
-# Copy this file to .env and fill in both values.
+# Copy this file to .env and fill in the two required values.
+# XAI_API_KEY is optional — Claude scripts work without it.
 # .env is gitignored. This file is committed so the next person knows what to set.
 
 # From platform.claude.com -> Settings -> API Keys
 ANTHROPIC_API_KEY=""
 
 # From weatherapi.com/signup.aspx (free tier, no credit card)
 WEATHER_API_KEY=""
+
+# From console.x.ai (optional — only the Grok lesson scripts need this)
+XAI_API_KEY=""

.github/workflows/ci.yml

@@ -24,9 +24,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        # 20.x is the supported floor (--env-file arrived in 20.6);
-        # 22.x is what the tutorial is written against.
-        node: ['20.x', '22.x']
+        # 22 is the supported floor (openai requires it). 24 is current LTS.
+        node: ['22.x', '24.x']
 
     steps:
       - uses: actions/checkout@v4

.gitignore

@@ -2,3 +2,5 @@ node_modules/
 .env
 usage.csv
 .DS_Store
+.grok/worktrees/
+.claude/worktrees/

.grok/README.md

@@ -0,0 +1,54 @@
+# `.grok/` — Grok Build project surface
+
+Portable Grok configuration for this repository. **Checked into git** so any
+clean clone shares the same contracts after `git pull`.
+
+Claude Code continues to use `.claude/` and `~/.claude/`. The two drivers are
+deliberately namespaced; see `skills/xmission/references/dual-driver.md`.
+
+## What is tracked
+
+| Path | Purpose |
+|------|---------|
+| `skills/xmission/` | **`/xmission`** — Grok mission contract (provision → execute → decommission) |
+| `rules/dual-driver.md` | Always-on coexistence with Claude Code |
+| `scripts/landed.sh` | Per-file land check used by `/xmission end` (no `~/.claude` dependency) |
+| `README.md` | This file |
+
+User-global Grok memory (when enabled): `~/.grok/memory/MEMORY.md` (not in this repo).
+
+## What is not tracked
+
+| Path | Why |
+|------|-----|
+| `.grok/worktrees/`, `.claude/worktrees/` | Long-lived mission checkouts; local to each machine |
+| root `.env*` / `node_modules/` | Secrets and installs (already ignored repo-wide) |
+
+Root `.gitignore` encodes the worktree roots. **Never `git clean -x` on main**
+while any worktree exists — ignored mission dirs are still live checkouts
+(`git worktree list` first).
+
+## Dual machine
+
+- **Pull the repo** — skills and rules appear under `.grok/` automatically.
+- **Worktrees are not synced.** On the other machine: `git fetch`, then either
+  re-attach with `git worktree add .grok/worktrees/wt-<ref>-<stream> <branch>`
+  for a pushed branch, or provision fresh with `/xmission`.
+- **Branches are shared** via `origin`. Push the mission branch before switching
+  machines if you intend to continue there.
+- No home paths are **depended on** for xmission to run (docs may mention
+  `~/.claude/…` as do-not-touch references only).
+
+## Invoke
+
+In a Grok Build session rooted at this repo:
+
+```
+/xmission <issue# | pr# | description>
+/xmission end
+```
+
+Natural language (“run an xmission for …”) should load the same skill.
+
+Claude’s `/mission` remains Claude’s (user/global command). Do not treat it as
+Grok law unless the operator says so.

.grok/rules/dual-driver.md

@@ -0,0 +1,22 @@
+# Dual-driver rules (Grok + Claude)
+
+Always on for Grok sessions in this repo. Claude sessions get the same table via
+root `CLAUDE.md`. Detail: `.grok/skills/xmission/references/dual-driver.md`.
+
+1. **Operator owns the merge.** Never merge a PR or claim ship authority unless the
+   operator explicitly orders it.
+2. **`@claude` on PRs is the operator’s clean review process** when a
+   mention-triggered workflow exists. Do not post `@claude` unprompted. Do not
+   overwrite Claude review comments. Fix findings when directed.
+3. **Namespaces**
+
+   | Driver | Worktrees | Branches | Port range |
+   |--------|-----------|----------|------------|
+   | Grok | `.grok/worktrees/` | `x/<type>/…` | **4000–4999** (`4000 + ref%1000`, then free-port bump) |
+   | Claude | `.claude/worktrees/` | house scheme | **3000–3999** (`3000 + ref%1000`) |
+
+4. **One owner per kickoff.** The other driver may babysit or review read-only.
+5. **Main checkout is integration ground** for both drivers. Feature commits only
+   in a mission worktree. Dirt on main is never yours to clean. Never
+   `git clean -x{d,f}` while any worktree exists (`git worktree list` first).
+6. Full contract: `.grok/skills/xmission/` (`/xmission`).

.grok/scripts/landed.sh

@@ -0,0 +1,91 @@
+#!/usr/bin/env bash
+# Repo copy for Grok /xmission decommission (tracked under .grok/scripts/).
+# Portable — no home-dir dependency. Usage:
+#   .grok/scripts/landed.sh <branch> origin/<default>
+#
+# Exit 0 = fully landed and safe to decommission. Exit 1 = something is unlanded.
+# Exit 2 = bad args / missing refs / internal git failure.
+#
+# Does NOT fetch. Callers must `git fetch origin` first so origin/<default> is current.
+#
+# Why a script (not a one-liner): the inline forms were wrong three times —
+#   1. Ancestry (`branch --merged`, `git log --not <base>`) false-positives on
+#      squash-merged branches (squash rewrites the commit).
+#   2. Plain two-dot `git diff <base> <branch>` false-positives as soon as the
+#      base moves; cannot tell "mine never landed" from "someone else's did".
+#   3. `git rev-parse "ref:path" 2>/dev/null || echo none` — on a missing path
+#      rev-parse prints its ARGUMENT, so two ABSENT deletions look unequal forever.
+#      `--verify --quiet` (or empty ls-tree) is the fix.
+# Hardened further (PR #63 review):
+#   4. core.quotePath can C-quote non-ASCII paths → rev-parse misses both sides →
+#      ABSENT==ABSENT false "landed". Use quotePath=false + NUL-delimited names.
+#   5. Blob-only compare misses mode-only changes (chmod). Compare ls-tree mode+sha.
+#   6. Rename detection collapses rename to destination only — use --no-renames so
+#      the deletion half of a half-landed rename is still checked.
+#   7. Pathspecs are glob-matched by default: a path with [ ] * ? can match a
+#      sibling file on both refs → false "landed". Use pathspec magic :(literal).
+#   8. git diff in a process substitution hides its exit status from pipefail;
+#      a failed diff leaves touched=0 and would exit 0. Capture first, check status.
+#
+# Property: for each path the branch touched relative to the merge base, the tree
+# entry (mode + blob sha) on BRANCH equals that on BASE; absent is first-class.
+set -uo pipefail
+
+BRANCH="${1:-$(git rev-parse --abbrev-ref HEAD)}"
+BASE="${2:-origin/main}"
+
+git rev-parse --verify --quiet "$BRANCH" >/dev/null || { echo "no such branch: $BRANCH" >&2; exit 2; }
+git rev-parse --verify --quiet "$BASE"   >/dev/null || { echo "no such base: $BASE"    >&2; exit 2; }
+
+base_commit=$(git merge-base "$BASE" "$BRANCH") || exit 2
+
+# $1=ref $2=path -> "mode sha" or ABSENT
+# :(literal) so [ ] * ? in the path are not pathspec wildcards.
+entry() {
+  local out
+  out=$(git ls-tree "$1" -- ":(literal)$2" 2>/dev/null) || true
+  if [ -z "$out" ]; then
+    echo ABSENT
+    return
+  fi
+  # ls-tree line: <mode> <type> <sha>\t<path>
+  # One path with :(literal) should yield at most one line; take first fields only.
+  printf '%s\n' "$out" | awk '{ print $1 " " $3; exit }'
+}
+
+# Capture NUL-delimited path list first so a failed diff cannot look like "nothing
+# changed" (process substitution would hide git's exit status from pipefail).
+paths_tmp=
+paths_tmp=$(mktemp) || { echo "mktemp failed" >&2; exit 2; }
+trap 'rm -f "$paths_tmp"' EXIT
+
+git -c core.quotePath=false diff -z --name-only --no-renames "$base_commit" "$BRANCH" >"$paths_tmp"
+diff_status=$?
+if [ "$diff_status" -ne 0 ]; then
+  echo "git diff failed (exit $diff_status) — cannot decide landed state" >&2
+  exit 2
+fi
+
+unlanded=0
+touched=0
+while IFS= read -r -d '' f; do
+  [ -n "$f" ] || continue
+  touched=$((touched + 1))
+  if [ "$(entry "$BRANCH" "$f")" = "$(entry "$BASE" "$f")" ]; then
+    echo "landed:   $f"
+  else
+    echo "UNLANDED: $f"
+    unlanded=$((unlanded + 1))
+  fi
+done <"$paths_tmp"
+
+if [ "$touched" -eq 0 ]; then
+  echo "no files differ from the merge base — $BRANCH is contained in $BASE"
+fi
+
+if [ "$unlanded" -eq 0 ]; then
+  echo "OK: $touched file(s) checked, all landed on $BASE"
+  exit 0
+fi
+echo "STOP: $unlanded of $touched file(s) not on $BASE — do not decommission"
+exit 1