Repo hygiene: fill stack-and-commands, normalize workplan statuses

- Fill .claude/rules/stack-and-commands.md (was an empty TODO template)
- Normalize workplan frontmatter statuses to canonical vocabulary
  (completed/done -> finished) per ADR-001

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

.claude/rules/stack-and-commands.md

@@ -1,19 +1,13 @@
 ## Stack
 
-<!-- TODO: Fill in language, frameworks, and key dependencies -->
+- **Language:** documentation and reusable CI/CD / platform templates (no application code yet)
-- **Language:**
+- **Key deps:** none at present — S4 layer is largely unpopulated
-- **Key deps:**
 
 ## Dev Commands
 
 ```bash
-# TODO: Fill in the standard commands for this repo
+make help   # only target currently defined
-
-# Install dependencies
-
-# Run tests
-
-# Lint / type check
-
-# Build / package (if applicable)
 ```
+
+No build, test, or deploy commands exist yet. When S4 work starts (CI/CD
+templates, SDKs, buildpacks), fill this file in the same change.