crosscheck: mechanical consistency across the yukart repos

Decisions, topics, doc references, deployed binaries and front matter, each
checked against the repo that owns the fact. A reusable workflow runs it from
every repo on push.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DDwfd6Ki8UfG4hK6W5YpJz

README.md

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+---
+type: reference
+---
+# Crosscheck
+
+Part of **Project Yukart**, making an old 2008 Mitsubishi Z27AG a bit smarter with modern technologies.
+
+Mechanical consistency checks across every yukart repository. A fact stated in
+more than one repo (a decision's status, a topic, a service list, a path in
+another repo's docs) is checked against the one place that owns it. No model,
+no network: plain Python over the tracked files.
+
+| Check | Source of truth | Catches |
+|---|---|---|
+| `decision` | project-yukart `docs/ARCHITECTURE.md`, decisions table | a decision number that does not exist; a line calling an Accepted decision proposed |
+| `topic` | contracts `schema/topics.json`, `schema/signals.json` | a `yukart/...` topic matching no pattern; a vehicle or host signal that is not registered, or has the wrong source |
+| `docref` | the repos' own trees | ``<repo> `FILE.md` `` naming a file that does not exist; relative markdown links that do not resolve |
+| `binaries` | each repo's `Cargo.toml` and `deploy/*.service` | project-yukart `REPOS.md` missing a deployed binary; `ORIN-RUNTIME.md` missing a deployed service |
+| `frontmatter` | the docs convention | a `docs/**/*.md` without front matter, or with an unknown `type` |
+
+## Run it
+
+```bash
+python3 crosscheck.py ~/dev/yukart        # the directory holding the repos side by side
+```
+
+Findings print as `repo/path:line: [check] message`; exit status 1 if any.
+
+## In CI: every repo, on every push
+
+`.gitea/workflows/crosscheck.yml` is a reusable workflow. Each yukart repo carries
+[`caller/crosscheck.yml`](caller/crosscheck.yml) as its own
+`.gitea/workflows/crosscheck.yml`. On a push it clones every repo of the org at
+`master`, puts the pushed repo at the pushed commit, and runs the script. A finding
+fails that push's run: the commit that made two repos disagree is the one marked.
+
+A new repo is checked as soon as it exists in the org; it needs the caller only to
+trigger checks on its own pushes.
+
+## Adding to it
+
+- **A false positive** is fixed in the rule, not silenced per line. Shapes that look
+  like topics but are not (Flutter channel names, systemd directories) are listed in
+  `NOT_TOPIC`; test-only topic roots in `IGNORED_TOPIC_ROOTS`.
+- **A new check** reads a source of truth that already exists in some repo. If the
+  fact has no single owner yet, give it one first; a check between two copies only
+  says that they differ, not which is right.