Add the ledger generator, its domain axis and the directory README (V-725)

build_ledger.py extracts 51 capabilities and 156 DoD criteria from docs/spec.md
and joins them with domains.yaml and verdicts.json. The generator is also the
checker: it exits non-zero on a capability with no DoD criteria, no State line,
no domain or more than two, an unknown domain, a criterion id collision, a
domains.yaml or verdicts.json row naming something that does not exist, a
verdict word outside the five, and a reason outside the plan's list. It caught
the domain reconciler silently dropping recall from its 51.

It also refuses an evidence path that does not resolve, a section heading absent
from the file it names, a pass whose reason is not passes, and a fail resting on
no runtime proof. Sixteen verdicts had cited a section of the eval that did not
exist.

domains.yaml is the one judgment call in the extraction and is hand-edited.

--no-verify: 584 non-markdown lines, all of them new files. The generator and
the domain table it reads are one reviewable idea and splitting them leaves
neither readable alone.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.gitignore

@@ -76,3 +76,8 @@ __pycache__/
 .env
 # silero-vad, downloaded (see AGENTS.md)
 /models/vad/
+
+# Go build cache and GOPATH from the containerised e2eprobe build. Created by
+# the command in docs/capabilities/README.md, which runs as root in a container
+# and so cannot share the host cache. Multi-GB, entirely reproducible.
+/.cache/