fix(acp): accept https:// URIs in image content blocks

[truenorth-lj]

Problem

packages/opencode/src/acp/agent.ts:1394 reads:

} else if (part.uri && part.uri.startsWith("http:")) {

This prefix check matches http://... URLs but not https://... URLs ("http:" is a literal 5-character prefix; "https://..." does not start with that exact substring because position 4 is s not :).

Every other URL check in the same codebase uses both prefixes:

File	Pattern
packages/opencode/src/session/instruction.ts:146,168	startsWith("https://") || startsWith("http://")
packages/opencode/src/cli/cmd/import.ts:98	startsWith("http://") || startsWith("https://")
packages/opencode/src/tool/webfetch.ts:23	!startsWith("http://") && !startsWith("https://")
packages/opencode/src/config/config.ts:1270	startsWith("http://") || startsWith("https://")

Only acp/agent.ts:1394 is missing https://. It looks like a typo (probably meant to write "http://" but the second / was dropped).

Reproducer

Send an ACP session/prompt request with an image content block whose uri is https://:

{
  "type": "image",
  "uri": "https://storage.googleapis.com/bucket/img.png",
  "mimeType": "image/png"
}

Expected: image part is forwarded to the LLM provider as a file part.
Actual: the case falls through (no parts.push), and the image is silently dropped from the prompt — no error, no warning.

This is the most likely path for any ACP client doing two-stage uploads (e.g. signing a GCS or S3 URL and sending the URL rather than inlining base64), because cloud-storage signed URLs are always https://.

Fix

One-line: align with the other 5 URL checks in this codebase by accepting both http:// and https:// prefixes explicitly.

-          } else if (part.uri && part.uri.startsWith("http:")) {
+          } else if (part.uri && (part.uri.startsWith("http://") || part.uri.startsWith("https://"))) {

Tests

I haven't added a unit test in this PR because I couldn't find an existing test for the surrounding case "image" block that I could extend. Happy to add one if you'd like — point me at the right test file pattern.

Out of scope

This is a typo fix — no behavior change for http:// URIs or for inline-data blocks. No new dependencies.

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