docs: make project instructions self-contained

[dangazineu]

The committed project instructions and one package README named private sibling repositories and pointed at their internal source paths, which only make sense to someone with access to those repos. This removes those references and reframes the surrounding prose in neutral terms so the docs read cleanly for an outside contributor cloning just this repo. No behavior or public API changes.

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What changed

• CLAUDE.md
  • "What this repo is" now frames the SDK as a client over the CodeSpar API (default endpoint api.codespar.dev) that also runs against a self-hosted runtime via baseUrl, instead of naming a private backend repo.
  • The VISION pointer is now a generic "read the project VISION" line — the private-repo link, name, and internal status/date are gone.
  • The wire-contract note keeps the 1:1 method-to-route discipline but drops the internal route path; it now says to keep the TS types, the Python package, and the backend in lockstep.
  • The Repository Map lists only the public repos, plus one neutral line noting a private managed tier serves the same session contract.
  • Package inventory and coding-convention lines reference "the backend" / "the managed backend" rather than a repo name or path.
  • Dropped a stale reference to a personal onboarding doc.
• packages/api-types/README.md
  • "Both the backend and the dashboard import from here" no longer names the private repos.

Not touched

SDK API surface, package inventory, wire-contract discipline, publishing ceremony, tech stack, conventions, workflow, and quick commands are all intact. Docs-only; no code, tests, or public API affected.