docs: refresh example release notices and links

[qw-in]

Remove some stale notices and update console links.

[arcjet-review]

Arcjet Review — 🟢 Low Risk

Decision: Approved

Rationale: This is a documentation-only PR that (1) replaces app.arcjet.com with console.arcjet.com across example READMEs, .env*.example files, and code comments/error messages, and (2) removes three stale [!IMPORTANT] notices in the eve-agent, mastra-agent, nextjs-guard-policy, and node-guard-policy READMEs about unpublished packages. No runtime logic changes, no dependency changes, no secrets exposed (the .env.example files only contain empty keys or placeholder ajkey_... values), and no auth/infra/migration triggers fire. The URL swap is applied consistently across all example projects.

Summary of Changes

Sweeping docs refresh across the examples/ directory: swaps app.arcjet.com → console.arcjet.com in READMEs, .env examples, code comments, error messages, and Vercel deploy URLs (the demo-image parameter), and removes stale release notices in four agent/guard-policy examples that referenced unpublished @arcjet/guard integrations.

Notes

PR touches ~95 files but each change is one of two mechanical edits (URL swap or removal of an identical [!IMPORTANT] block). Total diff size (~450 lines) is well under the 1000-line threshold.

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