fix(capture): warn 300–799px PNG floor; hard-block only below 300

Split FLOOR_WARN_PX=800 / FLOOR_BLOCK_PX=300. Warn-band still encodes and
includes the photo (Photos-ready + batchApply ok+warn). Block excludes
siblings and clean cal. CAPTURE-105 / CAPTURE.md / PHOTOS.md updated.

frontend/src/capture/session.overlay.test.ts

@@ -185,7 +185,8 @@ test('test(photos): Calculate stores overlayPng on results, clean inventory unto
       encodeN++;
       return {
         blob: new Blob([`clean-${encodeN}`], { type: 'image/png' }),
-        sourceBelowFloor: false,
+        sourceBelowBlock: false,
+        sourceBelowWarn: false,
       };
     },
   } as Parameters<typeof createCaptureSession>[0]);
@@ -221,7 +222,8 @@ test('test(photos): single-photo batch still yields clean + overlayPng (#63)', a
     draft: store,
     encodeInventory: async () => ({
       blob: new Blob(['only-clean'], { type: 'image/png' }),
-      sourceBelowFloor: false,
+      sourceBelowBlock: false,
+        sourceBelowWarn: false,
     }),
   } as Parameters<typeof createCaptureSession>[0]);
 
@@ -243,7 +245,8 @@ test('test(photos): draft persists overlayPng alongside inventoryPng (#63)', asy
     draft: store,
     encodeInventory: async () => ({
       blob: new Blob(['draft-clean'], { type: 'image/png' }),
-      sourceBelowFloor: false,
+      sourceBelowBlock: false,
+        sourceBelowWarn: false,
     }),
   } as Parameters<typeof createCaptureSession>[0]);