docs: add generate-context prompt to workflow documentation

Update README.md to include the generate-context prompt as an optional
pre-setup step in the SDD workflow:

- Add "Optional Pre-Setup" section explaining when and why to use generate-context
- Update workflow overview from 3 to 4 prompts
- Include generate-context in TLDR, Workflow Essentials, and usage examples
- Add SYSTEM.md to Core Artifacts section
- Position generate-context as first-time/existing codebase analysis tool

This aligns documentation with the workflow diagram showing optional
pre-setup for reverse-engineering existing context.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: iaminawe

README.md

@@ -23,20 +23,28 @@
     uvx --from git+https://github.com/liatrio-labs/spec-driven-workflow sdd-generate-commands generate --yes
     ```
 
-2. In your AI tool of choice, use `/generate-spec` with your idea:
+2. *(Optional, first time)* Run `/generate-context` to analyze your existing codebase:
+
+    ```text
+    /generate-context
+    ```
+
+    → AI analyzes your codebase → Context document created in `docs/001-SYSTEM.md`
+
+3. In your AI tool of choice, use `/generate-spec` with your idea:
 
     ```text
     /generate-spec I want to add user authentication to my app
     ```
 
     → AI asks clarifying questions → You provide answers → Spec created in `tasks/0001-spec-user-auth.md`
 
-3. Continue the flow:
+4. Continue the flow:
 
     - Run `/generate-task-list-from-spec` → Task list created in `tasks/tasks-0001-spec-user-auth.md`
     - Use `/manage-tasks` → Execute tasks one-by-one with proof artifacts
 
-4. **SHIP IT** 🚢💨
+5. **SHIP IT** 🚢💨
 
 ## Highlights
 
@@ -62,19 +70,38 @@ MCP technology remains available as an optional integration, but the heart of th
 
 All prompts live in `prompts/` and are designed for use inside your preferred AI assistant.
 
+### Optional Pre-Setup
+
+**`generate-context`** (`prompts/generate-context.md`): **Optional first step** for analyzing existing codebases before starting spec development. Use this when:
+- Working with an existing codebase the AI hasn't seen before
+- Need to understand repository architecture, patterns, and conventions
+- Want to document technical decisions and design rationale
+- Setting up context for multiple specs in the same project
+
+This prompt performs comprehensive codebase analysis and generates a `docs/00N-SYSTEM.md` file documenting architecture, tech stack, patterns, and conventions that inform all subsequent spec development.
+
+### Core SDD Workflow
+
 1. **`generate-spec`** (`prompts/generate-spec.md`): Ask clarifying questions, then author a junior-friendly spec with demoable slices.
 2. **`generate-task-list-from-spec`** (`prompts/generate-task-list-from-spec.md`): Transform the approved spec into actionable parent tasks and sub-tasks with proof artifacts.
 3. **`manage-tasks`** (`prompts/manage-tasks.md`): Coordinate execution, update task status, and record outcomes as you deliver value.
 
-Each prompt writes Markdown outputs into `tasks/`, giving you a lightweight backlog that is easy to review, share, and implement.
+Each prompt writes Markdown outputs into `tasks/` or `docs/`, giving you a lightweight backlog that is easy to review, share, and implement.
 
 ## How does it work?
 
 The workflow is driven by Markdown prompts that function as reusable playbooks for the AI agent. Reference the prompts directly, or invoke them via supported tooling, to keep the AI focused on structured outcomes. Users can manage context with their existing workflows (GitHub CLI, Atlassian MCP, etc.), and optionally let the MCP server automate portions of the process.
 
 ## Workflow Overview
 
-Three prompts in `/prompts` define the full lifecycle. Use them sequentially to move from concept to completed work.
+Four prompts in `/prompts` define the full lifecycle. Use them sequentially to move from concept to completed work.
+
+### Optional Pre-Setup — Generate Codebase Context ([prompts/generate-context.md](./prompts/generate-context.md))
+
+- **When to use:** Working with an existing codebase or starting multiple specs in the same project
+- **What it does:** Analyzes existing codebase architecture, extracts patterns and conventions, and documents technical decisions
+- **Output:** Creates `docs/00N-SYSTEM.md` with comprehensive codebase context that informs all subsequent spec generation
+- **Skip when:** Starting a greenfield project or the AI already has sufficient context about your codebase
 
 ### Stage 1 — Generate the Spec ([prompts/generate-spec.md](./prompts/generate-spec.md))
 
@@ -133,8 +160,9 @@ sequenceDiagram
 
 ## Core Artifacts
 
-- **Specs:** `000X-spec-<feature>.md` — canonical requirements, demo slices, and success metrics.
-- **Task Lists:** `tasks-000X-spec-<feature>.md` — parent/subtask checklist with relevant files and proof artifacts.
+- **Codebase Context (Optional):** `docs/00N-SYSTEM.md` — comprehensive codebase analysis documenting architecture, patterns, conventions, and technical decisions that inform spec development.
+- **Specs:** `tasks/000X-spec-<feature>.md` — canonical requirements, demo slices, and success metrics.
+- **Task Lists:** `tasks/tasks-000X-spec-<feature>.md` — parent/subtask checklist with relevant files and proof artifacts.
 - **Status Keys:** `[ ]` not started, `[~]` in progress, `[x]` complete, mirroring the manage-tasks guidance.
 - **Proof Artifacts:** URLs, CLI commands, screenshots, or tests captured per task to demonstrate working software.
 
@@ -144,6 +172,7 @@ The SDD workflow can be used in three ways, from simplest to most automated:
 
 ### Option 1: Manual Copy-Paste (No Tooling Required)
 
+0. **Optional: Generate codebase context (first time only):** If working with an existing codebase, copy or reference `prompts/generate-context.md` to analyze the repository and generate a comprehensive context document in `/docs`. This step helps the AI understand your codebase architecture and patterns for all subsequent specs.
 1. **Kick off a spec:** Copy or reference `prompts/generate-spec.md` inside your preferred AI chat. Provide the feature idea, answer the clarifying questions, and review the generated spec before saving it under `/tasks`.
 2. **Plan the work:** Point the assistant to the new spec and walk through `prompts/generate-task-list-from-spec.md`. Approve parent tasks first, then request the detailed subtasks and relevant files. Commit the result to `/tasks`.
 3. **Execute with discipline:** Follow `prompts/manage-tasks.md` while implementing. Update statuses as you work, attach proof artifacts, and pause for reviews at each demoable slice.
@@ -194,6 +223,7 @@ Run the prompts as an MCP server for programmatic access. This option is most us
 
 ### Workflow Essentials
 
+0. **(Optional, first time)** Run `/generate-context` or open `prompts/generate-context.md` to analyze your codebase and generate architecture documentation in `docs/`.
 1. Open `prompts/generate-spec.md` inside your AI assistant and follow the instructions to produce a new spec in `tasks/`.
 2. Point the assistant at the generated spec and run `prompts/generate-task-list-from-spec.md` to create the implementation backlog.
 3. Use `prompts/manage-tasks.md` while executing work to keep status, demo criteria, and proof artifacts up to date.