Update claude-api skill: Managed Agents August launch wave (#1532)

Mirror the latest bundled-skill content for the August 5 Managed Agents
launch wave:

- Session budgets: budget object at session create (minor-unit cents
  string), budget_reached pause semantics, settle-event allowlist,
  session.usage event, change/remove-to-resume, multiagent shared cap
- Deployment budgets: same budget object on deployments, copied onto
  each fired session, clearable and re-addable
- Inference geo pinning: inference_geo on the agent model object,
  per-session override, roster uniformity, never grandfathered
- Skills from a GitHub repository: root .claude/skills discovery at
  session start (cloud sandboxes only), trust-boundary warning
- Advisor: {type: "advisor", model} multiagent roster entry, reserved
  anthropic.advisor thread, plaintext vs redacted delivery; advisor
  tool max_uses/max_tokens/caching options and error result variant
- Multiagent: new when-to-use guidance (start with self, add cheaper
  workers, dedicated specialists), delegation tools, docs URL rename
- Corrections: agent versions are sequential integers, Files API
  uploads take a purpose param, stop_details refusal categories are an
  open set, Sonnet 5 added to the prefill-removed list, vault_ids is
  create-only on sessions, deployments gain an update endpoint

No-Verification-Needed: markdown-only skill content sync

skills/claude-api/shared/managed-agents-environments.md

@@ -71,6 +71,7 @@ Upload a file first via the Files API, then reference by `file_id` + `mount_path
 // 1. Upload
 const file = await client.beta.files.upload({
   file: fs.createReadStream("data.csv"),
+  purpose: "agent",
 });
 
 // 2. Attach as a session resource
@@ -116,6 +117,8 @@ This gives you a bidirectional file bridge: upload reference data in, download a
 
 Clones a GitHub repository into the session container during initialization, before the agent begins execution. The agent can read, edit, commit, and push via `bash` (`git`). Multiple repositories per session are supported — add one `resources` entry per repo. Repositories are cached, so future sessions that use the same repository start faster.
 
+Mounting a repository also loads any skills stored in its root `.claude/skills` directory — discovered once per session, from the repository state checked out at session start (cloud sandboxes only). See `shared/managed-agents-tools.md` → Skills from a GitHub repository.
+
 Repositories are attached for the lifetime of the session — to change which repositories are mounted, create a new session. You **can** rotate a repository's `authorization_token` on a running session via `client.beta.sessions.resources.update(resource_id, {session_id, authorization_token})`; the resource `id` is returned at session creation and by `resources.list()`.
 
 **Fields:**