feat: preflight - prerequisites checked and tool paths recorded before wikitool runs; launcher refuses without it (#151, POSIX half)

Files changed:
- .claude/settings.json
- .gitea/workflows/ci.yml
- .gitea/workflows/nightly.yml
- .gitea/workflows/release.yml
- .gitea/workflows/tracker-live.yml
- .github/hooks/wiki-trace.json
- .gitignore
- .vibe/hooks.toml
- AGENTS.md
- CHANGES.md
- EVALS.md
- INSTALL.md
- README.md
- VERSION
- instructions/bootstrap.md
- instructions/preflight.md
- instructions/setup-instance.md
- instructions/upgrade-instance.md
- tools/CONTRACT.md
- tools/README.md
- tools/chemenu/cli.py
- tools/chemenu/commands/dist_cmd.py
- tools/chemenu/commands/docs_verify.py
- tools/chemenu/commands/doctor.py
- tools/chemenu/commands/git_publish.py
- tools/chemenu/commands/migrate_cmd.py
- tools/chemenu/config.py
- tools/chemenu/corpus_cache.py
- tools/chemenu/prerequisites.py
- tools/chemenu/search/ripgrep.py
- tools/chemenu/tests/conftest.py
- tools/chemenu/tests/test_dist_upgrade.py
- tools/chemenu/tests/test_doctor.py
- tools/chemenu/tests/test_preflight.py
- tools/chemenu/toolpaths.py
- tools/preflight.sh
- tools/prerequisites.txt
- tools/run_wikitool.py
- tools/trace-hook
- tools/wikitool

tools/wikitool

@@ -1,25 +1,47 @@
-#!/usr/bin/env bash
-# Entry point for the wikitool CLI. Activates the local venv and runs the
-# chemenu package as a module so agents can invoke it via a stable path:
+#!/bin/sh
+# Entry point for the wikitool CLI, so agents and people invoke it through one
+# stable path on every platform:
 #
 #   tools/wikitool <command> [options]
 #
-# Setup (one time):
-#   cd tools
-#   python3 -m venv .venv
-#   .venv/bin/pip install -r requirements.txt
-set -euo pipefail
-DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+# This is the POSIX half - Linux, macOS and Git Bash on Windows. PowerShell 7
+# resolves the same string to tools/wikitool.ps1 first.
+#
+# Nothing here sets up an environment. tools/preflight.sh does that, once per
+# checkout and again after every stack update: it records the tool paths in
+# .wikitool-tools.json and creates tools/.venv. Until it has passed, this script
+# stops with exit 42 and names it - the preflight is the one step that must not
+# be skipped or improvised around (instructions/preflight.md).
+set -eu
+DIR=$(CDPATH='' cd -- "$(dirname -- "$0")" && pwd -P)
+ROOT=$(dirname -- "$DIR")
 
-if [ ! -x "$DIR/.venv/bin/python" ]; then
-  echo "wikitool: venv not found at $DIR/.venv" >&2
-  echo "Run: cd tools && python3 -m venv .venv && .venv/bin/pip install -r requirements.txt" >&2
-  exit 1
+# Both venv layouts: bin/ everywhere but Windows, Scripts\ there - which is also
+# what a venv created by a native Windows Python looks like from Git Bash.
+if [ -x "$DIR/.venv/bin/python" ]; then
+  PY="$DIR/.venv/bin/python"
+elif [ -f "$DIR/.venv/Scripts/python.exe" ]; then
+  PY="$DIR/.venv/Scripts/python.exe"
+else
+  PY=""
+fi
+
+if [ -z "$PY" ] || ! grep -q '"complete": true' "$ROOT/.wikitool-tools.json" 2>/dev/null; then
+  cat >&2 <<'EOF'
+STOP - this checkout is not set up yet (or no longer after an update).
+Run the preflight first; it checks what this computer has, records the tool
+paths and creates tools/.venv:
+
+  tools/preflight.sh
+
+It exits 0 when everything is in place. If it exits 42, show its output to the
+user as it is and wait - it says what to do. See instructions/preflight.md.
+EOF
+  exit 42
 fi
 
 # Do NOT cd into $DIR: that would resolve relative CLI arguments (e.g.
 # --markdown "kb/Lint Report.md") against tools/ instead of the caller's cwd.
-# Add $DIR to PYTHONPATH instead so `chemenu` is importable regardless of
-# where this script is invoked from.
-export PYTHONPATH="$DIR${PYTHONPATH:+:$PYTHONPATH}"
-exec "$DIR/.venv/bin/python" -m chemenu.cli "$@"
+# Running a script puts its own directory on sys.path, which is how `chemenu`
+# becomes importable without PYTHONPATH (whose separator differs on Windows).
+exec "$PY" "$DIR/run_wikitool.py" "$@"