Update claude-api skill: scheduled deployments, vault env-var credentials, system.message events (#1297)

- Add Managed Agents scheduled deployments: new
  shared/managed-agents-scheduled-deployments.md (cron schedules, deployment
  runs, pause/auto-pause), Deployments and Deployment Runs API reference,
  beta-header coverage, and SKILL.md routing
- Vault environment_variable credentials: secrets substituted at egress with
  networking allowlists; secrets guidance in tools, client-patterns, and
  onboarding docs rewritten around them; self-hosted sandbox caveats noted
- Add system.message event for mid-session system prompt updates (Opus 4.8
  only) to the events guide and API reference

skills/claude-api/SKILL.md

@@ -249,7 +249,7 @@ For placement patterns, architectural guidance, and the silent-invalidator audit
 
 **Mandatory flow:** Agent (once) → Session (every run). `model`/`system`/`tools` live on the agent, never the session. See `shared/managed-agents-overview.md` for the full reading guide, beta headers, and pitfalls.
 
-**Beta headers:** `managed-agents-2026-04-01` — the SDK sets this automatically for all `client.beta.{agents,environments,sessions,vaults,memory_stores}.*` calls. Skills API uses `skills-2025-10-02` and Files API uses `files-api-2025-04-14`, but you don't need to explicitly pass those in for endpoints other than `/v1/skills` and `/v1/files`.
+**Beta headers:** `managed-agents-2026-04-01` — the SDK sets this automatically for all `client.beta.{agents,environments,sessions,vaults,memory_stores,deployments,deployment_runs}.*` calls. Skills API uses `skills-2025-10-02` and Files API uses `files-api-2025-04-14`, but you don't need to explicitly pass those in for endpoints other than `/v1/skills` and `/v1/files`.
 
 **Subcommands** — invoke directly with `/claude-api <subcommand>`:
 
@@ -257,12 +257,14 @@ For placement patterns, architectural guidance, and the silent-invalidator audit
 |---|---|
 | `managed-agents-onboard` | Walk the user through setting up a Managed Agent from scratch. **Read `shared/managed-agents-onboarding.md` immediately** and follow its interview script: mental model → know-or-explore branch → template config → session setup → **pre-flight viability check** → emit code. The viability check (reconcile the stated job against configured tools/credentials/data) catches under-resourced setups — missing a tool, credential, or data access — before the agent burns budget. Do not summarize — run the interview. |
 
-**Reading guide:** Start with `shared/managed-agents-overview.md`, then the topical `shared/managed-agents-*.md` files (core, environments, tools, events, outcomes, multiagent, webhooks, memory, client-patterns, onboarding, api-reference). For Python, TypeScript, Go, Ruby, PHP, and Java, read `{lang}/managed-agents/README.md` for code examples. For cURL, read `curl/managed-agents.md`. **Agents are persistent — create once, reference by ID.** Store the agent ID returned by `agents.create` and pass it to every subsequent `sessions.create`; do not call `agents.create` in the request path. The Anthropic CLI (`ant`) is one convenient way to create agents and environments from version-controlled YAML — see `shared/anthropic-cli.md`. If a binding you need isn't shown in the language README, WebFetch the relevant entry from `shared/live-sources.md` rather than guess. C# has beta Managed Agents support via `client.Beta.Agents` and related namespaces.
+**Reading guide:** Start with `shared/managed-agents-overview.md`, then the topical `shared/managed-agents-*.md` files (core, environments, tools, events, outcomes, multiagent, webhooks, memory, scheduled-deployments, client-patterns, onboarding, api-reference). For Python, TypeScript, Go, Ruby, PHP, and Java, read `{lang}/managed-agents/README.md` for code examples. For cURL, read `curl/managed-agents.md`. **Agents are persistent — create once, reference by ID.** Store the agent ID returned by `agents.create` and pass it to every subsequent `sessions.create`; do not call `agents.create` in the request path. The Anthropic CLI (`ant`) is one convenient way to create agents and environments from version-controlled YAML — see `shared/anthropic-cli.md`. If a binding you need isn't shown in the language README, WebFetch the relevant entry from `shared/live-sources.md` rather than guess. C# has beta Managed Agents support via `client.Beta.Agents` and related namespaces.
 
 **When the user wants to set up a Managed Agent from scratch** (e.g. "how do I get started", "walk me through creating one", "set up a new agent"): read `shared/managed-agents-onboarding.md` and run its interview — same flow as the `managed-agents-onboard` subcommand.
 
 **When the user asks "how do I write the client code for X":** reach for `shared/managed-agents-client-patterns.md` — covers lossless stream reconnect, `processed_at` queued/processed gate, interrupt, `tool_confirmation` round-trip, the correct idle/terminated break gate, post-idle status race, stream-first ordering, file-mount gotchas, keeping credentials host-side via custom tools, etc.
 
+**When the user wants the agent to run on a schedule** (cron, "every night", "weekly report"): read `shared/managed-agents-scheduled-deployments.md` — deployments fire sessions autonomously on a cron cadence, with run records, retries, and auto-pause.
+
 
 ---