containers: pullEgressInterceptorImage uses name:tag@digest form — docker drops the tag, workerd then fails to find the image

### What versions & operating system are you using?

- wrangler: `4.84.1` (also reproduced on `4.72.0`)
- miniflare: `4.20260421.0`
- workerd: `1.20260421.1`
- Docker CE `29.4.1` (native daemon, not Docker Desktop)
- Ubuntu 24.04 / Linux 6.17.0

### Describe the Bug

On a host without `cloudflare/proxy-everything` pre-cached, a worker with containers + egress interception fails at runtime with:

```
✘ [ERROR] Uncaught Error: No such image available named cloudflare/proxy-everything:3cb1195@sha256:0ef6716c52430096900b150d84a3302057d6cd2319dae7987128c85d0733e3c8. Please ensure the container egress interceptor image is built and available.
```

…despite wrangler logging `⎔ Preparing container image(s)... / Downloaded newer image / ⎔ Container image(s) ready` during startup. The pull *appears* to succeed, but workerd still can't find the image.

### Root cause

[`pullEgressInterceptorImage`](https://github.com/cloudflare/workers-sdk/blob/main/packages/containers-shared/src/images.ts) invokes:

```ts
await runDockerCmd(dockerPath, ["pull", image, "--platform", "linux/amd64"]);
// image = "cloudflare/proxy-everything:3cb1195@sha256:0ef6716c52430096900b150d84a3302057d6cd2319dae7987128c85d0733e3c8"
```

When docker is handed a composite `name:tag@digest` reference, it fetches by digest and **silently drops the tag** — the image lands in the local store as an untagged entry, addressable only by digest. workerd then asks docker for the original `name:tag@digest` and gets "no such image" because there's no `name:tag` in the repo at all.

### Minimal reproduction

```
$ docker pull cloudflare/proxy-everything:3cb1195@sha256:0ef6716c52430096900b150d84a3302057d6cd2319dae7987128c85d0733e3c8 --platform linux/amd64
...
Status: Downloaded newer image for cloudflare/proxy-everything@sha256:0ef6716c52430096900b150d84a3302057d6cd2319dae7987128c85d0733e3c8
docker.io/cloudflare/proxy-everything:3cb1195@sha256:0ef6716c52430096900b150d84a3302057d6cd2319dae7987128c85d0733e3c8

$ docker images cloudflare/proxy-everything
IMAGE ID DISK USAGE CONTENT SIZE EXTRA
# (empty — no tagged image)

$ docker image inspect cloudflare/proxy-everything@sha256:0ef6716c52430096900b150d84a3302057d6cd2319dae7987128c85d0733e3c8 --format '{{.RepoTags}} {{.RepoDigests}}'
[] [cloudflare/proxy-everything@sha256:0ef6716c52430096900b150d84a3302057d6cd2319dae7987128c85d0733e3c8]
```

Note: `RepoTags=[]`. The `3cb1195` tag was not applied.

Confirming the workaround:

```
$ docker pull cloudflare/proxy-everything:3cb1195 --platform linux/amd64
...
$ docker images cloudflare/proxy-everything
cloudflare/proxy-everything:3cb1195 7cdb883de642 15.2MB
```

Now `wrangler dev` no longer hits the "No such image available" error.

### Impact

Any worker using containers with egress interception (e.g. `allowedHosts` / `interceptOutboundHttp`) breaks in `wrangler dev` on any host that didn't already have the `cloudflare/proxy-everything:3cb1195` tag cached. Cache-hit machines accidentally dodge the bug; clean machines hit it 100% of the time. This makes it flaky and hard to diagnose (the pull *looks* like it worked).

### Suggested fix

Either:

1. Drop the digest pinning from the pull command but keep it elsewhere (pull as `name:tag`, and keep the `name:tag@digest` form for workerd's lookup):
```ts
const pullRef = image.replace(/@sha256:[a-f0-9]+$/, "");
await runDockerCmd(dockerPath, ["pull", pullRef, "--platform", "linux/amd64"]);
```
Digest verification at pull time is lost, but workerd's lookup still pins by digest so content is still verified before use.

2. After pulling by digest, explicitly tag:
```ts
const digestOnly = image.replace(/:[^@]+@/, "@"); // strip the tag piece
const tagOnly = image.replace(/@sha256:[a-f0-9]+$/, "");
await runDockerCmd(dockerPath, ["pull", digestOnly, "--platform", "linux/amd64"]);
await runDockerCmd(dockerPath, ["tag", digestOnly, tagOnly]);
```

Happy to send a PR with whichever direction you prefer.

### Workaround

For anyone else hitting this while a fix is pending: miniflare reads `MINIFLARE_CONTAINER_EGRESS_IMAGE` as an override for both the pull and the workerd config. Setting it to just the tag (no digest) works around both halves of the bug:

```
export MINIFLARE_CONTAINER_EGRESS_IMAGE=cloudflare/proxy-everything:3cb1195
```

### Please provide any relevant error logs

```
[wrangler:info] ⎔ Preparing container image(s)...
docker.io/cloudflare/proxy-everything@sha256:0ef6716c52430096900b150d84a3302057d6cd2319dae7987128c85d0733e3c8: Pulling from cloudflare/proxy-everything
bc1da058f299: Pull complete
c27657e384b3: Pull complete
93bb89c5c4e0: Pull complete
Status: Downloaded newer image for cloudflare/proxy-everything@sha256:0ef6716c52430096900b150d84a3302057d6cd2319dae7987128c85d0733e3c8
⎔ Container image(s) ready
[wrangler:info] Ready on http://0.0.0.0:8788
✘ [ERROR] Uncaught Error: No such image available named cloudflare/proxy-everything:3cb1195@sha256:0ef6716c52430096900b150d84a3302057d6cd2319dae7987128c85d0733e3c8. Please ensure the container egress interceptor image is built and available.
Error checking if container is ready: connect(): Container ingress proxy is not running.
(repeats for every sandbox request)
```