Stamp metadata.anthropic_cookbook on managed-agent deploys

[dlaw-ant]

Adds metadata.anthropic_cookbook = "<repo-slug>/<cookbook-dir>" to every POST /v1/agents body the deploy script emits, so cookbook-sourced sessions become attributable in BigQuery.

Why: The agent's metadata is CMEK-excluded from the Werx→BQ mirror, so the only path to BQ is the session_agent_config_created canonical log. anthropics/anthropic#498619 (merged) taught EmitSessionConfigLog to emit this one reserved key; anthropics/dbt#9530 surfaces it as managed_agents_sessions.anthropic_cookbook. Without this stamp, cookbook sessions are indistinguishable from any other Managed Agents session.

What changed:

• REPO_SLUG derived from git config --get remote.origin.url (override via env) so the script stays copy-identical across vertical repos.
• COOKBOOK_TAG="${REPO_SLUG}/${ROLE}" — ROLE is the script's existing $1 cookbook-dir arg.
• One jq merge in create_agent() injects {anthropic_cookbook: $COOKBOOK_TAG} into .metadata (preserving any existing metadata keys). Applies to orchestrator and all subagents, and shows in --dry-run output.
• Echo the tag alongside the agent id on success.

Value format: <repo-slug>/<cookbook-dir> — e.g. financial-services/gl-reconciler. Matches the SanitizeAnthropicCookbook regex gate in api-go (^[a-z0-9._/-]{1,128}$).

Validation:

scripts/deploy-managed-agent.sh gl-reconciler --dry-run | jq '.[].metadata'
# → {"anthropic_cookbook":"financial-services/gl-reconciler"}