Arkiv 0.2.1: anonymous connection attribution

Adds a shared package-version and host header to the existing Arkiv MCP connection. Claude uses a local fixed-header helper and supports ARKIV_TELEMETRY=off; Codex sends a documented static header. No environment value, installation/session ID, local path, prompt, SDK state or skill-use counter is transmitted by this attribution.

Skills, project rules and context hooks are unchanged. The helper reads no files, performs no network request and adds no agent context. Node 20+ is required for the Claude rules hook and header helper. Existing MCP operation telemetry and hosting logs have their own privacy limits.

Verified: 39 serial tests, generated/import/static checks, strict Claude validation, actual Claude/Codex header connections against a local fixture, and anonymous public branch installation with exact bundle-byte parity in fresh isolated profiles. The required user plugin configurations and Codex config are unchanged; an additional global Claude metadata hash changed during the window and remains unattributed. The companion MCP passes classified preview response comparisons and uploaded-source verification; production promotion follows separately.

New context hooks, a fresh complete hook ablation, production skill-use collection and dashboard panels remain pending. See the README privacy section and the preserved historical qualifications in docs/verification.md.