chore: rename boundary command to agent-firewall (#25889)

Renames the `coder boundary` CLI subcommand to `coder agent-firewall` as
part of the Boundaries → Agent Firewall rebrand.

`coder boundary` is retained as a hidden, deprecated alias that prints a
deprecation notice to stderr before running. Both commands use separate
builder functions backed by the same boundary base command and license
verification logic.

Closes https://linear.app/codercom/issue/AIGOV-236

<details><summary>Implementation notes</summary>

**Approach:** Two separate `*serpent.Command` objects (not `Aliases`) so
the deprecated `boundary` path can print a stderr warning while
`agent-firewall` stays clean.

**Changes:**
- `enterprise/cli/boundary.go`: Split old `boundary()` into
`buildAgentFirewallCmd()` and `buildBoundaryAliasCmd()`. Error messages
in `verifyLicense` now reference "agent-firewall".
- `enterprise/cli/root.go`: Register both commands.
- `cli/root.go`: Update YAML-only option validation bypass for the new
command name.
- Tests: Rename to `TestAgentFirewallSubcommand`, add
`TestBoundaryAlias`, update license verification tests to use
`agent-firewall`.
- Golden files and CLI reference docs regenerated.
- `docs/ai-coder/agent-firewall/version.md` and `docs/manifest.json`
updated.

</details>

> Generated with [Coder Agents](https://coder.com/agents) by @SasSwart

docs/reference/cli/agent-firewall.md

@@ -1,12 +1,12 @@
 <!-- DO NOT EDIT | GENERATED CONTENT -->
-# boundary
+# agent-firewall
 
 Network isolation tool for monitoring and restricting HTTP/HTTPS requests
 
 ## Usage
 
 ```console
-coder boundary [flags] [args...]
+coder agent-firewall [flags] [args...]
 ```
 
 ## Description

docs/reference/cli/index.md

@@ -66,7 +66,7 @@ Coder — A tool for provisioning self-hosted development environments with Terr
 | [<code>support</code>](./support.md)                         | Commands for troubleshooting issues with a Coder deployment.                                                                 |
 | [<code>server</code>](./server.md)                           | Start a Coder server                                                                                                         |
 | [<code>provisioner</code>](./provisioner.md)                 | View and manage provisioner daemons and jobs                                                                                 |
-| [<code>boundary</code>](./boundary.md)                       | Network isolation tool for monitoring and restricting HTTP/HTTPS requests                                                    |
+| [<code>agent-firewall</code>](./agent-firewall.md)           | Network isolation tool for monitoring and restricting HTTP/HTTPS requests                                                    |
 | [<code>features</code>](./features.md)                       | List Enterprise features                                                                                                     |
 | [<code>licenses</code>](./licenses.md)                       | Add, delete, and list licenses                                                                                               |
 | [<code>groups</code>](./groups.md)                           | Manage groups                                                                                                                |