docs: scrub remaining internal repo + tooling references

- README.md: drop "first Sulkta Rust project — workout for crafting-
  table's Rust toolchain" paragraph + the `ci-runner build aldabra`
  recipe. Both reference non-public internal infrastructure.
- Dockerfile: drop "Built nightly on the build host (see infra-repo/scripts/
  build.sh)" comment + the `registry.example.com:5000/aldabra/mcp`
  internal image-name advertisement.
- Cargo.toml: drop the comment block referencing the deleted
  `docs/internal-build-rewrites.md` + `ci-runner + the build host + dev
  hosts` internal-builds note. The patch block stands on its
  own.

Cargo.toml

@@ -100,12 +100,6 @@ rpassword = "7"
 # in). Patches all pallas-* crates so the version graph resolves
 # consistently against the same commit. PR upstream pending; switch back
 # to crates.io once merged.
-#
-# Source URLs point at the public github mirror so external clones build
-# out of the box. Sulkta-internal builds short-circuit to the LAN gitea
-# via a `git config url.*.insteadOf` rewrite — no network egress, same
-# locked SHA. See `docs/internal-build-rewrites.md` for the one-line
-# config that wires that up on the build host + ci-runner + dev hosts.
 [patch.crates-io]
 pallas-codec      = { git = "https://github.com/Sulkta-Coop/pallas.git", branch = "feat-aux-data" }
 pallas-crypto     = { git = "https://github.com/Sulkta-Coop/pallas.git", branch = "feat-aux-data" }