Merge the three repositories into one monorepo

nisse-core's history becomes the repo root; the spec moves to docs/ at
top level; nisse-dev and nisse-ops fold in as package directories, their
seed histories (pointer files only) discarded. Pointer READMEs and
CLAUDE.mds are rewritten for in-tree paths.

Rationale: for a solo operator the three-repo split tripled admin
surface (tokens, CI, webhooks, permissions, backups) and imposed a
version-pinning contract on nisse-core, while the repo boundary was
never a trust boundary — the VM is. The spec's Part H is updated in the
next commit to record the decision.

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

nisse-dev/README.md

@@ -0,0 +1,8 @@
+# nisse-dev
+
+The Dev Agent: plans and implements software projects, produces Gitea PRs for human
+review, and reacts to review comments and commits. A thin application over the
+shared `nisse-core` library.
+
+**Part B** of the specification at [`../docs/Architecture-Build-Spec.md`](../docs/Architecture-Build-Spec.md)
+covers this agent; **Part A** covers the library it sits on.