docs: Add missing prompt commands + existing project walkthrough

[anchildress1]

This PR was generated using both GitHub Copilot and ChatGPT. Attribution is defined in each commit according standards defined in this blog post.

This addresses in part these issues: #472, #458, #472

I added a new Existing Project Guide that is originally written by ChatGPT, but later iterated with Copilot for a broader audience and more generic examples. I have a few more docs in mind for future PRs, Including a more detailed walkthrough, diagrams, and contributor flows. If there's anything else you can think of lmk!

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Copilot's Summary

This pull request introduces comprehensive improvements to the Spec-Kit documentation and methodology, making it easier for users to adopt Spec-Driven Development in both new and existing projects. The changes include a new guide for integrating Spec-Kit into existing codebases, clearer separation of workflows for new and existing projects, expanded documentation for all major commands, and enhanced navigation in the docs.

Documentation additions and workflow separation:

• Added a new existing-project-guide.md with a step-by-step, rollback-friendly process for integrating Spec-Kit into existing repositories. This guide details initialization, constitution setup, specification, planning, task breakdown, analysis, implementation, commit strategy, troubleshooting, and next steps.
• Updated quickstart.md to clarify its focus on new projects, added references to the new existing project guide, and expanded each step with more actionable instructions and example usage. [1] [2] [3] [4] [5] [6]

Expanded command documentation:

• Greatly expanded the methodology documentation in spec-driven.md to provide detailed explanations, expected inputs, minimal usage examples, and core values for all major Spec-Kit commands (/speckit.constitution, /speckit.specify, /speckit.clarify, /speckit.checklist, /speckit.plan, /speckit.tasks, /speckit.analyze, /speckit.implement). This makes it easier for users to understand the purpose and workflow of each command. [1] [2]

Navigation and organization:

• Updated the documentation table of contents (toc.yml) to include the new Existing Project Guide, improving discoverability and navigation between guides for different workflows.

User guidance and troubleshooting:

• Added troubleshooting sections and next steps to both guides, helping users resolve common issues and find further resources. [1] [2]

References: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]

[Copilot]

Pull Request Overview

This PR adds comprehensive documentation improvements to make Spec-Kit more accessible for both new and existing projects, expanding the command reference and establishing clearer user workflows.

• Enhanced documentation with detailed command descriptions, usage examples, and expected inputs/outputs
• Added a new Existing Project Guide for integrating Spec-Kit into established codebases
• Separated workflows between new projects (quickstart) and existing projects with distinct guides

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
docs/existing-project-guide.md	New comprehensive guide for adding Spec-Kit to existing projects with step-by-step workflow
docs/quickstart.md	Updated to focus on new projects, added constitution step, enhanced examples and next steps
docs/toc.yml	Added navigation entry for the new Existing Project Guide
spec-driven.md	Greatly expanded command documentation with detailed descriptions, benefits, usage examples, and expected inputs for all major commands

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[Copilot]

Pull Request Overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 10 comments.

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[localden]

@anchildress1 I like the direction of this, thank you for the contribution. Let's make sure that references to "Spec-Kit" are replaced with "Spec Kit".

[Copilot]

Pull Request Overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

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[anchildress1]

Hey @localden — hope you don't mind, Copilot was driving me insane so I added in a .github/copilot-instructions.md file that should redirect it to the existing ./AGENTS.md plus a new ./docs/AGENTS.md with a couple highlights specific to the published docs. Hopefully that's enough to calm my friend down a bit over here. 🤣🤞

[Copilot]

Pull Request Overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

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[localden]

@anchildress1 there actually isn't a need for copilot-instructions.md since Copilot (VS Code and the CLI) both respect AGENTS.md as-is.

[anchildress1]

@localden I added it for the automated code reviews that trigger Copilot once a PR is opened, which is one place that does not yet support AGENTS.md. The relative links to AGENTS.md should allow those files to be loaded into context within GitHub and it can easily be deleted without affecting anything after support for is enabled for reviews.

If it would help, I can add an explicit comment there to indicate its overall purpose. I left it out originally since Copilot reads the entire file into context. So comment or not that directive would still be considered by the agent. For what it is though, it's not likely to have a significant impact anyway. So, your call.