Give the crates a banner and a README in the same style, and bump them to 0.1.2

[ParallelEntrepreneur]

The crates.io pages now open like the repository: a banner, a badge row, then
what the crate is.

• assets/banners/banner.html draws both banners in colonizer.dev's colours and
  type: a mono eyebrow, a headline, a lead, a foot line and a diagram leading to
  the command.
  • colonizer-harness: "The mothership.", with the colony graph from the site,
    ending in colonizer.
  • colonizer-agentd: "Inside every colony.", showing a colony microVM with agentd
    between Claude Code, the event log and the terminal, and the private mesh up
    to the mothership.
• scripts/render-crate-banners.sh renders them at 2560×800 with headless Chrome
  into assets/banners/.png. The READMEs link them by their
  github.com/ghraw URL on main, because crates.io renders a README
  outside the repository.
• crates/colonizer/README.md and crates/colonizer-agentd/README.md:
  • banner and badges: crates.io version, latest release, docs, MIT;
  • what each crate is, with the install command, and why the crate alone isn't
    an install;
  • for the harness, what Colonizer does and the two crates;
  • for agentd, what it does and its four endpoints.
    The claims come from the README and docs/protocol.md §3.
• Both crates are at 0.1.2: crates.io shows a README only with a new version.
  Tagging v0.1.2 publishes them through Trusted Publishing.

cargo publish --dry-run packages and verifies both crates.