Docs site for stacks

[skarim]

Adds an Astro + Starlight documentation site under /docs, deployed to GitHub Pages via a new docs.yml workflow.

• Astro + Starlight project in docs/ with dev server, build, and preview scripts
• GitHub Actions workflow (.github/workflows/docs.yml) — builds on push to main and PRs touching docs/**, deploys to GitHub Pages
• 7 content pages: Home, Introduction / Overview, Quick Start, Working with Stacked PRs, Typical Workflows, CLI Reference, FAQs

[Copilot]

Pull request overview

Adds a new Astro + Starlight documentation site under /docs and a GitHub Actions workflow to build and deploy it to GitHub Pages, along with repository health files (SECURITY/SUPPORT/CONTRIBUTING/CODEOWNERS/CoC) and a few README updates.

Changes:

• Introduces an Astro/Starlight docs site (docs/) with styling, assets, and multiple content pages.
• Adds a dedicated GitHub Actions workflow to build and deploy the docs site to GitHub Pages.
• Adds repository community/policy docs and updates README CLI documentation (incl. gh stack alias).

Show a summary per file

File	Description
SUPPORT.md	Adds project support guidance.
SECURITY.md	Adds security reporting policy and contact info.
README.md	Updates quick start wording, adds gh stack alias docs, and adds repo metadata links (license/maintainers/support).
CONTRIBUTING.md	Adds contribution guidelines and local build/test instructions, including docs site instructions.
CODEOWNERS	Defines code ownership for the repository.
CODE_OF_CONDUCT.md	Adds Contributor Covenant Code of Conduct.
.github/workflows/release.yml	Normalizes workflow name casing (“Release”).
.github/workflows/docs.yml	Adds docs build/deploy workflow for GitHub Pages.
docs/package.json	Defines the docs site Node dependencies and scripts.
docs/package-lock.json	Locks docs dependency versions for reproducible installs.
docs/astro.config.mjs	Configures Astro/Starlight site settings, sidebar, and metadata.
docs/tsconfig.json	Adds TypeScript config for the Astro docs site.
docs/src/content.config.ts	Configures Starlight content collection loading/schema.
docs/src/styles/custom.css	Adds Starlight theme accent customization.
docs/src/content/docs/index.mdx	Adds the docs homepage content and example snippets.
docs/src/content/docs/introduction/overview.md	Adds an overview page explaining stacks and GitHub support.
docs/src/content/docs/getting-started/quick-start.md	Adds a quick start guide for installation and first usage.
docs/src/content/docs/guides/stacked-prs.md	Adds a practical guide for reviewing/merging/working with stacked PRs.
docs/src/content/docs/guides/ui.md	Adds a UI walkthrough guide with screenshots.
docs/src/content/docs/guides/workflows.md	Adds typical workflow patterns and examples.
docs/src/content/docs/reference/cli.md	Adds CLI command reference documentation.
docs/src/content/docs/faq.md	Adds an FAQ page for common questions.
docs/src/assets/stack-diagram.svg	Adds an SVG diagram used in the docs homepage.
docs/src/assets/screenshots/add-to-existing-stack.png	Adds UI screenshot asset(s) used by docs pages.
docs/src/assets/screenshots/create-first-pr.png	Adds UI screenshot asset(s) used by docs pages.
docs/src/assets/screenshots/create-pr-add-to-stack.png	Adds UI screenshot asset(s) used by docs pages.
docs/src/assets/screenshots/create-second-pr-stack-checkbox.png	Adds UI screenshot asset(s) used by docs pages.
docs/src/assets/screenshots/merge-box-failing-stack-requirements.png	Adds UI screenshot asset(s) used by docs pages.
docs/src/assets/screenshots/newly-created-stack.png	Adds UI screenshot asset(s) used by docs pages.
docs/src/assets/screenshots/selecting-branch-to-add.png	Adds UI screenshot asset(s) used by docs pages.
docs/src/assets/screenshots/stack-merge-box.png	Adds UI screenshot asset(s) used by docs pages.
docs/src/assets/screenshots/stack-navigator.png	Adds UI screenshot asset(s) used by docs pages.
docs/src/assets/screenshots/stacked-prs.png	Adds UI screenshot asset(s) used by docs pages.
docs/src/assets/screenshots/unstack-entire-stack.png	Adds UI screenshot asset(s) used by docs pages.
docs/public/favicon.svg	Adds a docs site favicon.
docs/public/robots.txt	Adds crawler directives for the docs site.
docs/.npmrc	Adds npm configuration for dependency installation.
docs/.gitignore	Adds docs-specific ignore rules (dist, .astro, node_modules, env files, etc.).

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• Files reviewed: 24/38 changed files
• Comments generated: 9

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