docs: Add the README banner from master

[BenWestgate]

What

Cherry-picks 4d7cf29 ("add README.md banner image", #83) from master with -x. It adds docs/images/python-codex32-banner.jpg and puts the banner line at the top of the v1 README.

Why

The banner is on master but not reviewability-v1. Bringing it over now means #94 won't conflict over the README later.

Notes

• This is a cherry-pick, not a merge. master has three other commits reviewability-v1 lacks (the 0.6.1 and 0.6.2 version bumps and efece7d). A merge would bring those in and would add a merge commit, which reviewability-v1's linear-history rule rejects.
• The commit keeps Ben as author; its message gains the standard (cherry picked from commit …) line.
• Land it by fast-forward to keep the hash.

Validation: the cherry-pick applied cleanly, and the diff is identical to 4d7cf29 (2 files, +2 lines). It changes no code.

🤖 Generated with Claude Code

https://claude.ai/code/session_013gZvwvuocM7a7Ut4kiBFHw

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Generated by Claude Code

[BenWestgate]

LGTM

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[BenWestgate]

AI-written (Claude), disclosed per docs/developer/AI_POLICY.md.

The github-advanced-security check failure isn't caused by this PR. That job runs GitHub's Copilot autofind reviewer, and it stopped before analysing anything: SessionModelError: You have exceeded your monthly quota (HTTP 402). This PR changes only the README and adds an image, so there's no code fix to make. Re-running won't help until the Copilot quota resets or is raised. The CodeQL checks are separate.

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Generated by Claude Code