[TSC-14] Add CLAUDE.md for docs repository

Add AI assistant guidance file documenting the repository structure,
purpose, and documentation conventions for the test-simple-calculator-docs repo.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -0,0 +1,55 @@
+# test-simple-calculator-docs
+
+AI-SDLC documentation repository containing the approved specification and Technical Architecture Document (TAD) for the Test Simple Calculator project.
+
+## Build Commands
+
+This is a documentation-only repository — there are no build steps, dependencies to install, or compilation required.
+
+## Test Commands
+
+No automated tests exist for this documentation repository.
+
+## Development Commands
+
+No dev server or REPL applies to this repository. To work with documentation:
+
+```bash
+# View the repository structure
+ls -R
+
+# Edit documentation files with any text editor
+```
+
+## Project Structure
+
+```
+test-simple-calculator-docs/
+├── README.md       — Repository overview and purpose
+└── CLAUDE.md       — This file; guidance for AI assistants
+```
+
+As documentation is added, the expected structure is:
+
+```
+test-simple-calculator-docs/
+├── README.md
+├── spec/           — Approved product/functional specification
+└── tad/            — Technical Architecture Document(s)
+```
+
+## Architecture Notes
+
+- This is a pure documentation repository with no source code, build system, or runtime dependencies.
+- It is part of an AI-SDLC (AI-assisted Software Development Lifecycle) workflow, meaning documents here are produced or reviewed with AI assistance and serve as authoritative design artifacts for the Test Simple Calculator implementation repository.
+- Documents should be kept in Markdown or a format agreed upon by the team.
+- The approved spec and TAD stored here drive implementation decisions in the corresponding code repository.
+
+## Code Style
+
+No code exists in this repository. For documentation files:
+
+- Use Markdown (`.md`) for all documents.
+- Follow standard Markdown conventions: ATX-style headings (`#`), fenced code blocks with language tags, and blank lines between sections.
+- Keep line length reasonable (80–120 characters) for readability in diffs.
+- No linter or formatter is configured; consistency with existing documents is the guideline.