Clarify roadmap and surface project banner

[FlyLikeAPenguin]

What changed

• move the workflow banner directly under the README title
• make the README point to the roadmap as the product-direction document
• replace the stale roadmap with shipped, now, next, and later sections
• add explicit future tracks for more log sources, sinks, Codex/agent backends, deployability, and operational maturity

Why

Potential users and contributors should see both the current value and a credible path beyond the initial Datadog + Claude CLI integration.

Validation

• pytest — 6 passed
• ruff check . — passed
• git diff --check — passed