Add language-neutral project onboarding

docs/USER_MANUAL.md

@@ -92,6 +92,32 @@ uv run pytest -q
 Use the executables under `/absolute/path/DocForge/.venv/bin/` when DocForge is not installed into
 the active shell environment.
 
+### Assess and onboard an unconfigured project
+
+Run a read-only assessment before writing configuration:
+
+```bash
+docforge --project-root /absolute/path/MyProject onboard
+```
+
+The result reports detected languages, build evidence, likely documentation, existing
+configuration, and capability status. Detection does not claim that a language frontend exists.
+Limit the assessment with one or more `--language` options when needed.
+
+Create, index, and render a generic starter manual explicitly:
+
+```bash
+docforge --project-root /absolute/path/MyProject onboard \
+  --language rust \
+  --scaffold \
+  --project-id my-project \
+  --title "My Project"
+```
+
+Scaffolding refuses to replace existing target files. It leaves source-graph status at
+`adapter_required` until a project integration implements and proves the adapter contract.
+See [Project onboarding](PROJECT_ONBOARDING.md) for the complete language-neutral checklist.
+
 ### Configure a generic project
 
 Create `/absolute/path/MyProject/.docforge/project.toml`: