docs: define initial Seriatim installation feature

README.md

@@ -16,12 +16,30 @@ only workspace documentation, planning, and shared development utilities.
 - [`docs/roadmap/features/`](docs/roadmap/features/) contains durable feature
   roadmaps for selected units of work.
 - [`docs/status.md`](docs/status.md) records current cross-repository progress.
-- [`docs/plans/template.md`](docs/plans/template.md) defines the staged format
-  used for out-of-band implementation.
+- [`docs/roadmap/implementation.md`](docs/roadmap/implementation.md), when
+  present, is the single active out-of-band implementation plan.
+- [`docs/roadmap/implementation-template.md`](docs/roadmap/implementation-template.md)
+  defines its staged format.
 
 Run `./scripts/status` to see the branch and working-tree state of every
 repository in the workspace manifest.
 
+## Development Tooling
+
+Create the shared workspace environment on Ubuntu 26.04 with:
+
+```sh
+sudo apt-get install python3-venv
+python3 -m venv .venv
+.venv/bin/python -m pip install --upgrade pip
+.venv/bin/python -m pip install -r requirements-dev.txt
+```
+
+Either activate it with `source .venv/bin/activate` or invoke tools directly,
+for example `.venv/bin/ansible-playbook` and `.venv/bin/ansible-lint`.
+Dependency upgrades are deliberate changes to `requirements-dev.txt`; do not
+install workspace development packages into the system Python environment.
+
 ## Repository Boundaries
 
 The directories ignored by this repository are intentional nested Git working