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>

README.md

@@ -1,16 +1,22 @@
-# nisse-core
+# Nisse
 
-The shared library both Nisse agents sit on (Part A of the specification), and the
-home of the system-level design documentation.
+Two self-hosted AI agents sharing a common library, named for the Nordic farm
+spirit that keeps the place running overnight and expects to be treated well in
+return.
 
-The library itself does not exist yet: it is extracted from `nisse-dev` once that
-agent works, at step 10 of the build order. Until then this repository carries the
-specification.
+| Package | Role |
+|---|---|
+| [`nisse-core/`](nisse-core/) | Shared library both agents sit on (Part A) |
+| [`nisse-dev/`](nisse-dev/) | Dev Agent — plans and implements software projects (Part B) |
+| [`nisse-ops/`](nisse-ops/) | Sysadmin Agent — operates infrastructure (Part C) |
+
+One repository, three packages. The library does not exist as code yet: it is
+extracted from `nisse-dev` once that agent works (build-order step 10), as a
+package split within this tree.
 
 ## Architecture
 
-    docs/Architecture-Build-Spec.md
-
-Covers the shared library (Part A), the Dev Agent `nisse-dev` (Part B), the Sysadmin
-Agent `nisse-ops` (Part C), the supporting services, the build order, and the
+The system-level specification lives at
+[`docs/Architecture-Build-Spec.md`](docs/Architecture-Build-Spec.md). It covers the
+shared library, both agents, the supporting services, the build order, and the
 remaining open decisions.