docs(readme): add octopus mascot hero and brand assets

[mgiovani]

What

Adds the crimson octopus brand mascot as the README hero (it doubles as the project logo), plus the derived brand assets.

The octopus was chosen from a brand-art exploration sweep (30 logos + 23 mascot concepts); its "eight arms, each holding a different tool" reads as many skills for AI agents. Codex then recolored the approved mascot into six palettes — crimson #E4363E won.

Changes

• README.md — centered hero banner at the top (reuses the social-preview card).
• assets/octopus.png — transparent mascot / logo (scrubbed, reads on light + dark).
• assets/octopus-favicon.png — head-crop favicon (the full mascot is illegible at 32px).
• assets/social-preview.png — 1280×640 OpenGraph card, reused as the README hero.

Notes

• No code touched; make check + make validate-plugins were green before branching.
• Follow-up (manual, no API): set the repo Social preview under Settings → General to assets/social-preview.png.

https://claude.ai/code/session_01VjJ7CCnodhW8SFED126UTT

[claude]

Review

Small, low-risk docs/branding PR — a hero image in the README plus two new brand assets. A few notes:

Unreferenced assets
assets/octopus.png (809 KB, 1078×1078) and assets/octopus-favicon.png (67 KB, 256×256) are added but not referenced anywhere in the repo (README, marketplace manifests, CI, etc.) — only social-preview.png is used. If they're meant for a future docs site favicon or for manual upload as the GitHub repo's "social preview" image, it'd help to say so in the PR description or a short comment, so a future contributor doesn't mistake them for dead weight and delete them.

Image size/weight
social-preview.png is 826 KB at 16-bit color depth for a 1280×640 image displayed at width="760" in the README. That's heavy for a hero image loaded on every README view — running it through pngquant/oxipng (or converting to 8-bit) would likely cut it by 70-90% with no visible quality loss. Same applies to octopus.png (809 KB) if it ends up embedded somewhere later.

CHANGELOG
Per AGENTS.md's contributing guidelines ("Update CHANGELOG.md for user-facing changes"), this doesn't have a [Unreleased] entry. Arguably optional for a branding-only change, but worth a one-liner for consistency with how other PRs in this repo have been tracked.

Everything else

• Alt text on the <img> is descriptive and appropriate.
• No functional code touched, so no test coverage gap.
• No security concerns — static binary assets, nothing executable or script-embedded.

Nothing blocking here — the visual addition itself is a nice touch for the README. Mainly flagging the unreferenced files and image weight for a quick follow-up.