Clarify ghost's brand context router positioning

[nahiyankhan]

Category: improvement
User Impact: New users can understand ghost, record one brand decision, and use it with their existing agent.

Problem: The READMEs mixed consumer setup with implementation detail and repeated the product thesis. Public descriptions also blurred the distinction between the agent selecting guidance and ghost delivering it.

Solution: Describe ghost as a brand context router for agents across GitHub, npm, and the site opening. Lead the READMEs with setup, a confirmed payment-failure rule that applies across email/errors/support, and reviewing the result; link out for technical detail. No CLI, API, or package-format behavior changes.

Validation:

• pnpm run quality:all: passed through the pre-push hook, including builds, package/release checks, workspace checks, and guidance validation.
• pnpm test: 332 passed, 1 skipped.
• README smoke checks: the exact guidance example validates; gather/pull/stats work; npm links target existing repo paths; consumer sections match after URL adaptation.
• Desktop (1280px) and mobile (375px) site inspection passed before the hero-line restoration. The restoration retains the original hero text/layout; docs build and typecheck pass.
• git diff --check: passed. Existing non-blocking lint and cover-policy warnings remain unchanged.

Changeset: added .changeset/plain-readme.md as a patch for @design-intelligence/ghost.

ghost Review:

• Current CLI has no ghost check command; package validation passed through quality:all.
• node packages/ghost/dist/bin.js review --base origin/main --package apps/docs/.ghost --node principles --node composition --node visual-system: advisory packet assessed against the copy-only site changes. Typography, layout, materials, and motion remain unchanged.
• The packet reports material/check coverage gaps for metadata and docs outside the site's bindings, plus the existing unreferenced docs-site node. These are advisory coverage gaps, not failed checks.

File changes

• README.md: consumer-first walkthrough, router positioning, cross-task example, concise references.
• packages/ghost/README.md: same consumer story with absolute links for npm.
• apps/docs/src/components/Hero.astro: retain the original "likeliest thing" hero line, with router positioning and explicit agent-selection/CLI-delivery wording in the explanation below.
• apps/docs/src/layouts/Base.astro: align the default title and description.
• package.json and packages/ghost/package.json: align package descriptions without changing commands or dependencies.
• .changeset/plain-readme.md: release note for the public documentation update.

Screenshots/Demos: Desktop and mobile screenshots inspected locally; not attached. The README includes a runnable guidance example.