docs: clarify Sandboxes first-run policy setup (#26421)

## Summary

The getting-started walkthrough promised a network preset prompt on the
first sandbox run, even when policy was already configured. Explain when
the CLI prompts, document `sbx policy init balanced` for manual
initialization, and remove outdated prompt transcripts from the
walkthrough and local-policy page. Also clarify that agent kits can add
model-provider allowances under Locked Down.

@netlify /ai/sandboxes/get-started/

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content/manuals/ai/sandboxes/get-started.md

@@ -53,27 +53,15 @@ $ cd ~/my-project
 $ sbx run --name my-sandbox claude
 ```
 
-The first time you run a sandbox, the CLI prompts you to choose a default
-network preset:
+In an interactive terminal, the CLI prompts you to choose a preset if the
+global network policy hasn't been initialized. Select **Balanced** to permit traffic to common development
+services while blocking other destinations unless you approve them. If a policy
+is already configured, the CLI uses it without prompting.
 
-```plaintext
-Initialize the global network policy for your sandboxes:
-
-  Applies to all sandboxes, current and future — change it later with
-  "sbx policy allow/deny/rm". Kits, including built-in agent kits, may
-  also add per-sandbox rules.
-
-     1. Open         — All network traffic allowed, no restrictions.
-  ❯  2. Balanced     — Default deny, with common dev sites allowed.
-     3. Locked Down  — All network traffic blocked unless you allow it.
-
-  Use ↑/↓ or 1–3 to navigate, Enter to confirm, Esc to cancel.
-```
-
-**Balanced** is a good starting point — it permits traffic to common
-development services while blocking everything else. You can adjust individual
-rules later. See [Local policy](governance/access-controls/local.md) for a full
-description of each option.
+To initialize the policy without an interactive prompt, run
+`sbx policy init balanced` before `sbx run`. See
+[Local policy](governance/access-controls/local.md) for the available presets
+and how to change an existing policy.
 
 Replace `claude` with the agent you want to use — see [Agents](agents/) for the
 full list.
@@ -122,8 +110,8 @@ when running several agents on one repository — use
 ## Control what the agent can reach
 
 Isolation isn't only about the filesystem. You also control what the sandbox
-can reach on the network. You chose a default policy before the sandbox
-started, and you can inspect or adjust it at any time.
+can reach on the network. You can inspect or adjust the active policy at any
+time.
 
 Check which rules are in effect:
 
@@ -137,9 +125,9 @@ To allow a specific host:
 $ sbx policy allow network registry.npmjs.org
 ```
 
-With **Locked Down**, even your model provider API is blocked unless you
-explicitly allow it. With **Balanced**, common development services are
-permitted by default. See
+With Balanced, common development services are permitted by default. With
+Locked Down, destinations need an allow rule from you or a kit. Built-in agent
+kits can add rules for their model providers. See
 [local policy](governance/access-controls/local.md) for the full rule set
 and how to customize it.
 

content/manuals/ai/sandboxes/governance/access-controls/local.md

@@ -37,24 +37,21 @@ with a hostname rule (for example, `sbx policy allow network "myhost:22"`) or an
 address-based rule. UDP requires the experimental feature and policy rules
 described in [Allow outbound UDP](#allow-outbound-udp). ICMP is blocked.
 
-If you haven't chosen a default preset, the CLI prompts you before it runs a
-sandbox. Running `sbx policy reset` clears the preset and prompts you to choose
-again:
+If the global network policy hasn't been initialized, the CLI prompts you to
+choose a preset when you run a sandbox in an interactive terminal. If a policy
+is already configured, including one carried over from an earlier installation,
+the CLI uses it without prompting.
 
-```plaintext
-Initialize the global network policy for your sandboxes:
+To initialize the policy without an interactive prompt, run:
 
-  Applies to all sandboxes, current and future — change it later with
-  "sbx policy allow/deny/rm". Kits, including built-in agent kits, may
-  also add per-sandbox rules.
-
-     1. Open         — All network traffic allowed, no restrictions.
-  ❯  2. Balanced     — Default deny, with common dev sites allowed.
-     3. Locked Down  — All network traffic blocked unless you allow it.
-
-  Use ↑/↓ or 1–3 to navigate, Enter to confirm, Esc to cancel.
+```console
+$ sbx policy init balanced
 ```
 
+Available values are `allow-all`, `balanced`, and `deny-all`. Initialization is
+a one-time setup. To change an existing preset, use
+[`sbx policy reset`](#resetting).
+
 | Preset      | Description                                                                                                                                       |
 | ----------- | ------------------------------------------------------------------------------------------------------------------------------------------------- |
 | Open        | All outbound TCP traffic is allowed. Equivalent to adding a wildcard allow rule with `sbx policy allow network "**"`. |
@@ -95,9 +92,9 @@ workflows. Run `sbx policy ls` to see exactly which rules it includes.
 
 ### Non-interactive environments
 
-In non-interactive environments such as CI pipelines or headless servers, the
-interactive prompt can't be displayed. Use `sbx policy init` to set the
-preset before running any other `sbx` commands:
+In non-interactive environments such as CI pipelines or headless servers, an
+uninitialized policy causes `sbx run` to return an error. Use `sbx policy init`
+to set the preset before running a sandbox:
 
 ```console
 $ sbx policy init balanced