Align root tooling and linting

[dshevtsov]

Purpose of this pull request

This pull request (PR) aligns the repository root tooling and linting with current Adobe Developer Platform (ADP) DevSite conventions, turns on alternate text for images in Markdown lint rules, and updates pattern library and style guide topics so figures use descriptive alt text. It also adds generated site metadata files used by the platform and tightens .gitignore and GitHub Pages workflow notes.

Summary

• Tooling: Replaced the local Express-based dev.mjs dev server with adp-devsite-utils (dev, navigation/redirect/metadata/contributor helpers, expanded runLint and link-check scripts). Removed legacy package.json config.sitePath and the express dev dependency.
• Lint: Added .markdownlint-cli2.jsonc (gitignore-aware ignores). Updated .markdownlint.yml—notably enabled MD045 (image alt text), adjusted duplicate-heading and MDX allowlists for components, and aligned table pipe rules with team defaults.
• Content: Swapped bare ![](...) image syntax for ![...](...) with short descriptive alt text across affected pattern library and style guide design pages.
• Site assets: Added src/pages/adp-site-metadata.json and src/pages/contributors.json for ADP site integration.
• Repo hygiene: Refreshed .gitignore (e.g. package-lock.json, build/super-linter artifacts, .claude/) and documented GitHub Pages source requirements in the deploy workflow.

Affected pages

Site base: https://developer.adobe.com/commerce/admin-developer (from src/pages/config.md pathPrefix).

Because many topics were touched for image alt text, listing section hubs plus representative pages:

• Design pattern library
• Style guide — design

Pattern library topics with content updates (image accessibility):

• Static content
• Slide-outs, modals, and overlays
• Buttons
• Button bar
• View controller
• Filters
• Tile
• Data table
• Tree
• Progress indicator
• Form elements
• Image uploader
• Date and time selector
• Row pattern (table)
• Select from list
• Use default config
• Iconography (graphics)
• Links
• Wizard
• Scheduled changes module
• Timeline dashboard
• Address form
• Sign-in form

Style guide — design:

• Color
• Iconography
• Page grids

Infrastructure-only (no direct reader-facing doc rewrites beyond the above): .github/workflows/deploy-github-pages.yml, package.json, .gitignore, .markdownlint.yml, .markdownlint-cli2.jsonc, src/pages/adp-site-metadata.json, src/pages/contributors.json, removed dev.mjs.