CMMS fork: robust board-photo encoding for the AI bridge

read_board_image reported "no board photos available" - buildProjectImages
was returning [] (both photos failed to encode) with no visibility.

- split encodeImage into downscale() + blobToB64(); on any failure
  (createImageBitmap / canvas.toBlob returning null / EXIF-heavy JPEGs)
  fall back to sending the raw blob base64 if it's under ~3MB.
- coerce a non-Blob img.blob through new Blob([...]).
- per-image [cmms-pcb-bridge] tracing: "downscaled ok" / "downscale
  failed: <msg> - trying raw" / "raw encode also failed" etc.

docs/cmms-bridge.js

@@ -162,40 +162,69 @@
 
 	// The board photos live in pcb-retrace's IndexedDB (imported by the user or
 	// unpacked from the .pcbretrace.zip), NOT as CMMS attachments, so the
-	// assistant can't reach them with read_attachment_image. Downscale + JPEG
+	// assistant can't reach them with read_attachment_image. Hand them along
-	// each and hand them along with the buffer so a `read_board_image` tool can
+	// with the buffer so a `read_board_image` tool can surface them.
-	// surface them. Long edge ~1400px, quality 0.8 - a phone photo lands well
+	const MAX_IMG_B64 = 4 * 1024 * 1024; // ~3MB raw; matches message.php's cap
-	// under 300KB.
+
-	async function encodeImage(blob, maxEdge) {
+	function blobToB64(blob) {
-		const bmp = await createImageBitmap(blob);
+		return new Promise((res, rej) => {
-		const s = Math.min(1, maxEdge / Math.max(bmp.width, bmp.height));
-		const w = Math.max(1, Math.round(bmp.width * s));
-		const h = Math.max(1, Math.round(bmp.height * s));
-		const c = document.createElement('canvas');
-		c.width = w; c.height = h;
-		c.getContext('2d').drawImage(bmp, 0, 0, w, h);
-		bmp.close();
-		const out = await new Promise(res => c.toBlob(res, 'image/jpeg', 0.8));
-		const b64 = await new Promise((res, rej) => {
 			const r = new FileReader();
 			r.onload = () => res(String(r.result).split(',', 2)[1] || '');
-			r.onerror = rej;
+			r.onerror = () => rej(new Error('FileReader failed'));
-			r.readAsDataURL(out);
+			r.readAsDataURL(blob);
 		});
-		return { w, h, b64 };
+	}
+
+	// Downscale a photo to ~maxEdge on the long side as JPEG. Returns a Blob.
+	async function downscale(blob, maxEdge) {
+		const bmp = await createImageBitmap(blob);
+		try {
+			const s = Math.min(1, maxEdge / Math.max(bmp.width, bmp.height));
+			const w = Math.max(1, Math.round(bmp.width * s));
+			const h = Math.max(1, Math.round(bmp.height * s));
+			const c = document.createElement('canvas');
+			c.width = w; c.height = h;
+			c.getContext('2d').drawImage(bmp, 0, 0, w, h);
+			const out = await new Promise(r => c.toBlob(r, 'image/jpeg', 0.8));
+			if (!out) throw new Error('canvas.toBlob returned null');
+			return out;
+		} finally {
+			try { bmp.close(); } catch (e) {}
+		}
 	}
 
 	async function buildProjectImages() {
 		if (!currentBomId || !bomImages.length) return [];
 		const out = [];
 		for (const img of bomImages.slice(0, 6)) {
-			try {
+			let blob = img.blob;
-				const enc = await encodeImage(img.blob, 1400);
+			if (!(blob instanceof Blob)) {
-				if (enc.b64.length > 3 * 1024 * 1024) { trace('image too large after encode, skipping', img.id); continue; }
+				try { blob = new Blob([blob], { type: (img.type || 'image/jpeg') }); }
-				out.push({ id: img.id, name: img.name || (img.id + '.jpg'), mime: 'image/jpeg', data_base64: enc.b64 });
+				catch (e) { trace('image', img.id, 'has no usable blob'); continue; }
-			} catch (e) {
-				trace('image encode failed', img.id, e && e.message);
 			}
+			let b64 = null;
+			try {
+				b64 = await blobToB64(await downscale(blob, 1400));
+				trace('image', img.id, 'downscaled ok');
+			} catch (e) {
+				trace('image', img.id, 'downscale failed:', e && e.message, '- trying raw');
+				// Fall back to the raw blob (some builds / EXIF-heavy JPEGs break
+				// createImageBitmap or toBlob). Only if it's not huge.
+				try {
+					if (blob.size <= 3 * 1024 * 1024) b64 = await blobToB64(blob);
+					else trace('image', img.id, 'raw blob too large (', blob.size, ')');
+				} catch (e2) {
+					trace('image', img.id, 'raw encode also failed:', e2 && e2.message);
+				}
+			}
+			if (!b64) continue;
+			if (b64.length > MAX_IMG_B64) { trace('image', img.id, 'over size cap after encode'); continue; }
+			out.push({
+				id: img.id,
+				name: img.name || (img.id + '.jpg'),
+				mime: (blob.type && blob.type.indexOf('image/') === 0) ? blob.type : 'image/jpeg',
+				data_base64: b64,
+			});
 		}
 		trace('buildProjectImages:', out.length, 'of', bomImages.length, 'photos encoded');
 		return out;