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/CONTRACT.md

@@ -54,14 +54,15 @@ file end to end is for changing the CLI itself.
 
 Full bootstrap for a fresh clone - including publishing the skills, which are not
 committed - is [`instructions/bootstrap.md`](../instructions/bootstrap.md). The
-environment alone:
+environment alone is the preflight ([`instructions/preflight.md`](../instructions/preflight.md)),
+from the repo root:
 
 ```bash
-cd tools
-python3 -m venv .venv
-.venv/bin/pip install -r requirements.txt
+tools/preflight.sh
 ```
 
+Until it has passed, every `tools/wikitool` call exits 42 and names it.
+
 ## Usage
 
 Run from the repo root:
@@ -3220,6 +3221,8 @@ Check that this instance is correctly configured.
 **NOTES**
 
 - Checks dependencies (Python, ripgrep), author resolution, stack version, git identity/branch/remote, published skills, the kb/raw/reports/work/instructions structure, and generated files.
+- Tool paths (`tool-paths`): `.wikitool-tools.json` written by a preflight that finished, every tool `tools/prerequisites.txt` names for this platform recorded, and every recorded path still there - a `FAIL` otherwise, fixed by running `tools/preflight.sh` again.
+- Install folder (`install-dir`): on Windows with long paths off, a `FAIL` when the folder holding `tools/` is longer than `tools/prerequisites.txt` allows (95 characters) - the limit the preflight enforces before it sets anything up.
 - Personalization: `USER.md`/`SOUL.md` present **and** filled - a file still carrying the template's sentinel is a `FAIL`.
 - KB conventions: `kb/CONVENTIONS.md` present, unsentinelled, and naming all three tool-owned section headings - a `FAIL` on any of the three.
 - Environment note: `ENVIRONMENT.md` is optional, so absent is `OK`; a still-templated one is a `WARN`.
@@ -3235,6 +3238,7 @@ Check that this instance is correctly configured.
 **SEE ALSO**
 
 - `instructions/setup-instance.md` - the setup steps most findings point back to
+- `instructions/preflight.md` - what `tool-paths` and `install-dir` point back to
 - `INSTALL.md` § "Konfiguration" - the per-checkout configuration files
 - `EVALS.md` - telemetry state and caps
 - `instructions/session-setup.md` - setting `WIKITOOL_SESSION_ID`