feat: full image support across all channels (#725)

* feat: full image support across all channels

End-to-end image handling: upload, generation, analysis, editing, and
rendering across web gateway, HTTP webhook, WASM (Telegram/Slack), and
REPL channels. Builds on the attachment infrastructure from #596 and
draws inspiration from PR #641's image pipeline approach — credit to
that PR's author for the sentinel JSON pattern and base64-in-JSON
upload design.

Key changes:
- Image upload in web UI (file picker, paste, preview strip)
- Image generation tool (FLUX/DALL-E via /v1/images/generations)
- Image edit tool (multipart /v1/images/edits with fallback)
- Image analysis tool (vision model for workspace images)
- Model detection utilities (image_models.rs, vision_models.rs)
- Sentinel JSON detection in dispatcher for generated image rendering
- StatusUpdate::ImageGenerated → SSE/WS/REPL/WASM broadcast
- HTTP webhook attachment support (base64, 5MB/file, 10MB total)
- WASM channel image download (Telegram via file API, Slack via host HTTP)
- Tool registration wiring in app.rs

[skip-regression-check]

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: address PR #725 review comments (16 issues)

- SecretString for API keys in all image tools (image_gen, image_edit, image_analyze)
- Binary image read via tokio::fs::read instead of DB-backed workspace.read()
- Replace Arc<Workspace> with Option<PathBuf> base_dir (workspace has no filesystem API)
- ApprovalRequirement::UnlessAutoApproved for cost-sensitive image tools
- Scope sentinel detection to image_generate/image_edit tool names only
- Skip ToolResult preview broadcast for image sentinels (avoids multi-MB base64 in SSE)
- Extract shared media_type_from_path() to builtin/mod.rs
- Rename fallback_chat_edit → fallback_generate with tracing::warn
- Increase gateway body limit from 1MB to 10MB for image uploads
- Increase webhook body limit to 15MB (base64 overhead)
- Log warning on invalid base64 in images_to_attachments
- Client-side image size limits (5MB/file, 5 images max) in app.js
- aria-label on attach button for accessibility
- Update body_too_large test for new 10MB limit

[skip-regression-check]

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: add Slack file size check before download (PR review item #15)

Skip downloading files larger than 20 MB in the Slack WASM channel to
avoid excessive memory use and slow downloads in the WASM runtime.
Logs a warning when a file is skipped. Also bumps channel versions
for Slack and Telegram (prior branch changes).

[skip-regression-check]

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* style: cargo fmt

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix(security): add path validation and approval requirement to image tools

Add sandbox path validation via validate_path() to both ImageAnalyzeTool
and ImageEditTool to prevent path traversal attacks that could exfiltrate
arbitrary files through external vision/edit APIs. Also fix
ImageAnalyzeTool::requires_approval to return UnlessAutoApproved,
consistent with ImageEditTool and ImageGenerateTool.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: post-download size guards and empty data_url sentinel check

- Slack: add post-download size check on actual bytes when metadata
  size_bytes is absent, preventing bypass of the 20MB limit
- Telegram: add 20MB download size limit (matching Slack) enforced
  in download_telegram_file() after receiving response bytes
- Dispatcher: skip broadcasting ImageGenerated SSE event when
  data_url is empty from unwrap_or_default(), log warning instead

Closes correctness issues #3, #4, #5 from PR #725 review.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: use mime_guess for media type detection, add alt attrs and media_type validation

- Replace hardcoded media type mapping with mime_guess crate (already in deps)
- Add alt attributes to img elements in web UI for accessibility
- Validate media_type starts with "image/" in images_to_attachments()
- Update bmp test assertion to match mime_guess behavior

Co-Authored-By: Claude Opus 4.6 <[email protected]>

---------

Co-authored-by: Claude Opus 4.6 <[email protected]>
Co-authored-by: Zaki <[email protected]>

channels-src/slack/Cargo.lock

@@ -267,7 +267,7 @@ dependencies = [
 
 [[package]]
 name = "slack-channel"
-version = "0.1.0"
+version = "0.2.1"
 dependencies = [
  "hex",
  "hmac",

channels-src/slack/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "slack-channel"
-version = "0.2.0"
+version = "0.2.1"
 edition = "2021"
 description = "Slack Events API channel for IronClaw"
 license = "MIT OR Apache-2.0"

channels-src/slack/src/lib.rs

@@ -357,10 +357,108 @@ fn extract_slack_attachments(files: &Option<Vec<SlackFile>>) -> Vec<InboundAttac
         .collect()
 }
 
+/// Download a file from Slack using the url_private endpoint.
+///
+/// Slack file downloads require Bearer auth with the bot token, which is
+/// injected by the host credential system via `channel_host::http_request`.
+fn download_slack_file(url: &str) -> Result<Vec<u8>, String> {
+    let headers = serde_json::json!({});
+
+    let result = channel_host::http_request("GET", url, &headers.to_string(), None, None);
+
+    let response = result.map_err(|e| format!("Slack file download failed: {}", e))?;
+
+    if response.status != 200 {
+        let body_str = String::from_utf8_lossy(&response.body);
+        return Err(format!(
+            "Slack file download returned {}: {}",
+            response.status, body_str
+        ));
+    }
+
+    Ok(response.body)
+}
+
+/// Download file bytes and store them via the host for processing.
+///
+/// Downloads all file types (images, documents, etc.) so the host-side
+/// middleware can process them (vision pipeline for images, text extraction
+/// for documents, transcription for audio, etc.).
+/// Maximum file size to download (20 MB). Files larger than this are skipped
+/// to avoid excessive memory use and slow downloads in the WASM runtime.
+const MAX_DOWNLOAD_SIZE_BYTES: u64 = 20 * 1024 * 1024;
+
+fn download_and_store_slack_files(attachments: &[InboundAttachment]) {
+    for att in attachments {
+        let Some(ref url) = att.source_url else {
+            continue;
+        };
+
+        // Skip files that exceed the size limit
+        if let Some(size) = att.size_bytes {
+            if size > MAX_DOWNLOAD_SIZE_BYTES {
+                channel_host::log(
+                    channel_host::LogLevel::Warn,
+                    &format!(
+                        "Skipping Slack file download: {} bytes exceeds {} MB limit (id={})",
+                        size,
+                        MAX_DOWNLOAD_SIZE_BYTES / (1024 * 1024),
+                        att.id
+                    ),
+                );
+                continue;
+            }
+        }
+
+        match download_slack_file(url) {
+            Ok(bytes) => {
+                // Post-download size guard: metadata size_bytes is optional,
+                // so a file with no size info could bypass the pre-download check.
+                if bytes.len() as u64 > MAX_DOWNLOAD_SIZE_BYTES {
+                    channel_host::log(
+                        channel_host::LogLevel::Warn,
+                        &format!(
+                            "Discarding Slack file after download: {} bytes exceeds {} MB limit (id={})",
+                            bytes.len(),
+                            MAX_DOWNLOAD_SIZE_BYTES / (1024 * 1024),
+                            att.id
+                        ),
+                    );
+                    continue;
+                }
+
+                channel_host::log(
+                    channel_host::LogLevel::Info,
+                    &format!(
+                        "Downloaded Slack file: {} bytes, mime={}",
+                        bytes.len(),
+                        att.mime_type
+                    ),
+                );
+                if let Err(e) = channel_host::store_attachment_data(&att.id, &bytes) {
+                    channel_host::log(
+                        channel_host::LogLevel::Error,
+                        &format!("Failed to store Slack file data: {}", e),
+                    );
+                }
+            }
+            Err(e) => {
+                channel_host::log(
+                    channel_host::LogLevel::Error,
+                    &format!("Failed to download Slack file: {}", e),
+                );
+            }
+        }
+    }
+}
+
 /// Handle a Slack event and emit message if applicable.
 fn handle_slack_event(event: SlackEvent, team_id: Option<String>, _event_id: Option<String>) {
     let attachments = extract_slack_attachments(&event.files);
 
+    // Download and store file attachments for host-side processing
+    download_and_store_slack_files(&attachments);
+
     match event.event_type.as_str() {
         // Direct mention of the bot (always in a channel, not a DM)
         "app_mention" => {
@@ -722,4 +820,10 @@ mod tests {
         let event: SlackEvent = serde_json::from_str(json).unwrap();
         assert!(event.files.is_none());
     }
+
+    #[test]
+    fn test_max_download_size_constant() {
+        // Verify the constant is 20 MB
+        assert_eq!(MAX_DOWNLOAD_SIZE_BYTES, 20 * 1024 * 1024);
+    }
 }