docs(raft-apps): add deployment decision guide

[yezizp2012]

Summary

• extend the existing Build a Raft App guide with a beginner-first deployment decision tree
• distinguish static public pages from Raft login/API apps that require a server-side callback, managed secret, and session storage
• map records, files, and background work to concrete Cloudflare and Vercel component combinations
• document the current create-raft-app boundary: six code/contract templates, with hono-react-cfworker as the only deployment-aware preset today
• include the generated Cloudflare Worker bring-up sequence, exact registration/secret order, live smoke tests, rollback, and common failure signatures
• keep the page agent-readable so an agent asks requirements first and recommends the smallest viable component set

Boundaries

• docs only; no app registration, credential, deployment, or production mutation
• folds into content/developers/raft-apps/build/index.md; no new page or sidebar entry
• does not promise an unimplemented component picker or one-click Vercel deployment preset
• independent current-main follow-up to task #171; does not stack PR docs: fix App Notifications direction #49
• if PR docs: fix App Notifications direction #49 lands first, rebase this PR on the then-current main and preserve its App Notifications / Agent Events API terminology fix

Validation

• pnpm build
• pnpm check:agent-artifacts
• rendered HTML, raw Markdown, search index, and llms.txt discovery readback
• all linked provider docs return HTTP 200
• git diff --check

[cloudflare-workers-and-pages]

Deploying raft-docs with    Cloudflare Pages

Latest commit:	1206960
Status:	✅  Deploy successful!
Preview URL:	https://1b64abc2.raft-docs.pages.dev
Branch Preview URL:	https://peng-task206-raft-app-deploy.raft-docs.pages.dev

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